[Transcriber's note: Image sizes are limited to the browser window size. To expand an image, right click on the image and select "view image" or "open image in new tab". Then click on the new image to see it full size. You could also just use you favorite image viewer directly.

Many projects are of contemporary interest—magic, kites and boomerangs for example. Try a "Querl" for starters.

There are many projects of purely historical interest, such as chemical photography, phonographs, and devices for coal furnaces.

Another class of projects illustrate the caviler attitude toward environment and health in 1913. These projects involve items such as asbestos, gunpowder, acetylene, hydrogen, lead, mercury, sulfuric acid, nitric acid, cadmium, potassium sulfate, potassium cyanide, potassium ferrocyanide, copper sulfate, and hydrochloric acid. Many references to these have been highlighted in red.

Projects requiring extra skill and care that involve high voltage, melting metals, or other hazards, have the title highlighted.

Please view these as snapshots of culture and attitude, not as suggestions for contemporary activity.

Be careful and have fun, or simply read and enjoy a trip into yesterday.]

The Boy Mechanic
Vol. 1
700 Things for Boys to Do
800 Illustrations Showing How

How to Make a Glider (See page 171)

How To Construct

Wireless Outfits, Boats, Camp Equipment,
Aerial Gliders, Kites,
Self-propelled Vehicles Engines, Motors,
Electrical Apparatus, Cameras
And
Hundreds Of Other Things Which Delight Every Boy

With 800 Illustrations

Copyrighted, 1913, By H. H. Windsor
Chicago
Popular Mechanics Co.
Publishers

Engine Details

The accompanying sketch illustrates a two-cylinder single-acting, poppet valve steam engine of home construction.

The entire engine, excepting the flywheel, shaft, valve cams, pistons and bracing rods connecting the upper and lower plates of the frame proper, is of brass, the other parts named being of cast iron and bar steel.

The cylinders, G, are of seamless brass tubing, 1-1/2 in. outside diameter; the pistons, H, are ordinary 1-1/2 in. pipe caps turned to a plug fit, and ground into the cylinders with oil and emery. This operation also finishes the inside of the cylinders.

The upright rods binding the top and bottom plates are of steel rod about 1/8-in. in diameter, threaded into the top plate and passing through holes in the bottom plate with hexagonal brass nuts beneath.

The valves, C, and their seats, B, bored with a countersink bit, are plainly shown. The valves were made by threading a copper washer, 3/8 in. in diameter, and screwing it on the end of the valve rod, then wiping on roughly a tapered mass of solder and grinding it into the seats B with emery and oil.

The valve rods operate in guides, D, made of 1/4-in. brass tubing, which passes through the top plate and into the heavy brass bar containing the valve seats and steam passages at the top, into which they are plug-fitted and soldered.

The location and arrangement of the valve seats and steam passages are shown in the sketch, the flat bar containing them being soldered to the top plate.

The steam chest, A, over the valve mechanism is constructed of 1-in. square brass tubing, one side being sawed out and the open ends fitted with pieces of 1/16 in. sheet brass and soldered in. The steam inlet is a gasoline pipe connection such as used on automobiles.

The valve-operating cams, F, are made of the metal ends of an old typewriter platen, one being finished to shape and then firmly fastened face to face to the other, and used as a pattern in filing the other to shape. Attachment to the shaft, N, is by means of setscrews which pass through the sleeves.

The main bearings, M, on the supports, O, and the crank-end bearings of the connecting rods, K, are split and held in position by machine screws with provision for taking them up when worn.

The exhausting of spent steam is accomplished by means of slots, I, sawed into the fronts of the cylinders at about 1/8 in. above the lowest position of the piston's top at the end of the stroke, at which position of the piston the valve rod drops into the cutout portion of the cam and allows the valve to seat.

All the work on this engine, save turning the pistons, which was done in a machine shop for a small sum, and making the flywheel, this being taken from an old dismantled model, was accomplished with a hacksaw, bench drill, carborundum wheel, files, taps and dies. The base, Q, is made of a heavy piece of brass.

The action is smooth and the speed high. Steam is supplied by a sheet brass boiler of about 3 pt. capacity, heated with a Bunsen burner.

Contributed by Harry F. Lowe, Washington, D. C.

Wax Hand on Board and Electrical Connections

The magic hand made of wax is given to the audience for examination, also a board which is suspended by four pieces of common picture-frame wire. The hand is placed upon the board and answers, by rapping, any question asked by members of the audience. The hand and the board may be examined at any time and yet the rapping can be continued, though surrounded by the audience.

The Magic Wand, London, gives the secret of this spirit hand as follows: The hand is prepared by concealing in the wrist a few soft iron plates, the wrist being afterwards bound with black velvet as shown in Fig. 1. The board is hollow, the top being made of thin veneer (Fig. 2). A small magnet, A, is connected to a small flat pocket lamp battery, B. The board is suspended by four lengths of picture-frame wire one of which, E, is connected to the battery and another, D, to the magnet. The other wires, F and G, are only holding wires. All the wires are fastened to a small ornamental switch, H, which is fitted with a connecting plug at the top. The plug can be taken out or put in as desired.

The top of the board must be made to open or slide off so that when the battery is exhausted a new one can be installed. Everything must be firmly fixed to the board and the hollow space filled in with wax, which will make the board sound solid when tapped.

In presenting the trick, the performer gives the hand and board with wires and switch for examination, keeping the plug concealed in his right hand. When receiving the board back, the plug is secretly pushed into the switch, which is held in the right hand. The hand is then placed on the board over the magnet. When the performer wishes the hand to move he pushes the plug in, which turns on the current and causes the magnet to attract the iron in the wrist, and will, therefore, make the hand rap. The switch can be made similar to an ordinary push button so the rapping may be easily controlled without detection by the audience.

Fig.1, 2, 3—Forming the skis

During the winter months everyone is thinking of skating, coasting or ski running and jumping. Those too timid to run down a hill standing upright on skis must take their pleasure in coasting or skating.

The ordinary ski can be made into a coasting ski-toboggan by joining two pairs together with bars without injury to their use for running and jumping. The ordinary factory-made skis cost from $2.50 per pair up, but any boy can make an excellent pair for 50 cents.

In making a pair of skis, select two strips of Norway pine free from knots, 1 in. thick, 4 in. wide and 7 or 8 ft. long. Try to procure as fine and straight a grain as possible. The pieces are dressed thin at both ends leaving about 1 ft. in the center the full thickness of 1 in., and gradually thinning to a scant 1/2 in. at the ends. One end of each piece is tapered to a point beginning 12 in. from the end. A groove is cut on the under side, about 1/4 in. wide and 1/8 in. deep, and running almost the full length of the ski. This will make it track straight and tends to prevent side slipping. The shape of each piece for a ski, as it appears before bending, is shown in Fig. 1.

The pointed end of each piece is placed in boiling water for at least 1 hour, after which the pieces are ready for bending. The bend is made on an ordinary stepladder. The pointed ends are stuck under the back of one step and the other end securely tied to the ladder, as shown in Fig. 2. They should remain tied to the ladder 48 hours in a moderate temperature, after which they will hold their shape permanently.

The two straps, Fig. 3, are nailed an a little forward of the center of gravity so that when the foot is lifted, the front of the ski will be raised. Tack on a piece of sheepskin or deer hide where the foot rests, Fig. 4.

Fig. 4—The Toe Straps

The best finish for skis is boiled linseed oil. After two or three applications the under side will take a polish like glass from the contact with the snow.

Fig. 5—Ski-Toboggan

The ski-toboggan is made by placing two pairs of skis together side by side and fastening them with two bars across the top. The bars are held with V-shaped metal clips as shown in Fig. 5.

Contributed by Frank Scobie, Sleepy Eye, Minn.

Fig. 1, Fig. 2—Inner Tube and Cover

Procure an inner tube of a bicycle tire, the closed-end kind, and fold it in four alternate sections, as shown in Fig. 1. Cut or tear a piece of cloth into strips about 1/2 in. wide, and knot them together. Fasten this long strip of cloth to the folded tube and weave it alternately in and out, having each run of the cloth about 4 in. apart, until it is bound as shown in Fig. 1. Make a case of canvas that will snugly fit the folded tube when inflated. The straps that hold the preserver to the body may be made of old suspender straps. They are sewed to the case at one end and fastened at the other with clasps such as used on overall straps. The tube can be easily inflated by blowing into the valve, at the same time holding the valve stem down with the teeth. The finished preserver is shown in Fig. 2.

Bending and Cutting the Wood

When the ice is too thin for skating and the snow is not right for skis, about the only thing to do is to stay in the house. A boomerang club will help to fill in between and also furnishes good exercise for the muscles of the arm. A boomerang can be made of a piece of well seasoned hickory plank. The plank is well steamed in a wash boiler or other large kettle and then bent to a nice curve, as shown in Fig. 1. It is held in this curve until dry, with two pieces nailed on the sides as shown.

After the piece is thoroughly dried out, remove the side pieces and cut it into sections with a saw, as shown in Fig. 2. The pieces are then dressed round. A piece of plank 12 in. wide and 2 ft. long will make six boomerangs. To throw a boomerang, grasp it and hold the same as a club, with the hollow side away from you. Practice first at some object about 25 ft. distant, and in a short time the thrower will be able to hit the mark over 100 ft. away. Any worker in wood can turn out a great number of boomerangs cheaply.

Contributed by J. E. Noble, Toronto, Ontario.

Laying the Snow Bricks

Playing in the snow can be raised to a fine art if boys and girls will build their creations with some attempt at architectural skill and not content themselves with mere rough work. Working in snow and ice opens a wide field for an expression of taste and invention, but the construction of houses and forts out of this plastic material provides the greatest amount of pleasure to the normally healthy boy or girl.

The snow house of the Eskimo is probably the unhealthiest of buildings made by any savage to live in, but it makes an excellent playhouse in winter, and represents at the same time a most ingenious employment of the arch system in building. The Eskimos build their snow houses without the aid of any scaffolding or interior false work, and while there is a keystone at the top of the dome, it is not essential to the support of the walls. These are self-supporting from the time the first snow blocks are put down until the last course is laid.

The snow house is of the beehive shape and the ground plan is that of a circle. The circle is first laid out on the ground and a space cleared for it. Then a row of snow blocks is laid on the ground and another course of similar blocks placed on top. The snow blocks are not exactly square in shape, but about 12 in. long, 6 in. high and 4 or 5 in. thick. Larger or smaller blocks can be used, according to size of the house and thickness of the walls.

First, the snow blocks must be packed and pressed firmly into position out of moist snow that will pack. A very light, dry snow will not pack easily, and it may be necessary to use a little water. If the snow is of the right consistency, there will be no trouble in packing and working with it. As most of the blocks are to be of the same size throughout, it will pay to make a mold for them by forming a box of old boards nailed together, minus the top, and with a movable bottom, or rather no bottom at all. Place the four sided box on a flat board and ram snow in it, forcing it down closely. Then by lifting the box up and tapping the box from above, the block will drop out. In this way blocks of uniform size are formed, which makes the building simpler and easier.

While one boy makes the blocks another can shave them off at the edges and two others can build the house, one inside of the circle and the other outside. The Eskimos build their snow houses in this way, and the man inside stays there until he is completely walled in. Then the door and a window are cut through the wall.

Each layer of snow blocks must have a slight slant at the top toward the center so that the walls will constantly curve inward. This slant at the top is obtained better by slicing off the lower surfaces of each block before putting it in its course. The top will then have a uniform inward slant.

The first course of the snow house should be thicker than the others, and the thickness of the walls gradually decreases toward the top. A wall, however, made of 6-in. blocks throughout will hold up a snow house perfectly, if its top is no more than 6 or 7 ft. above the ground. If a higher house is needed the walls should be thicker at the base and well up toward the middle.

The builder has no mortar for binding the blocks together, and therefore he must make his joints smooth and even and force in loose snow to fill up the crevices. A little experience will enable one to do this work well, and the construction of the house will proceed rapidly. The Eskimos build additions to their houses by adding various dome-shaped structures to one side, and the young architect can imitate them. Such dome-shaped structures are shown in one of the illustrations.

Three-Room Snow House

A fact not well understood and appreciated is that the Eskimo beehive snow house represents true arch building. It requires no scaffolding in building and it exerts no outward thrust. In the ordinary keystone arch used by builders, a, temporary structure must be erected to hold the walls up until the keystone is fitted in position, and the base must be buttressed against an outward thrust. The Eskimo does not have to consider these points. There is no outward thrust, and the top keystone is not necessary to hold the structure up. It is doubtful whether such an arch could be built of brick or stone without scaffolding, but with the snow blocks it is a simple matter.

Fig. 1, Fig. 2, Fig. 3—The Lock Parts

The sketch shows the construction of a lock I have on a door which is quite a mystery to those who do not know how it operates. It also keeps them out. The parts of the lock on the inside of the door are shown in Fig. 1. These parts can be covered so that no one can see them.

The ordinary latch and catch A are attached to the door in the usual manner. The latch is lifted with a stick of wood B, which is about 1 ft. long and 1 in. wide, and pivoted about two-thirds of the way from the top as shown. The latch A is connected to the stick B with a strong cord run through a staple to secure a right-angle pull between the pieces. A nail, C, keeps the stick B from falling over to the left. The piece of wood, D, is 6 or 8 in. long and attached to a bolt that runs through the door, the opposite end being fastened to the combination dial. Two kinds of dials are shown in Fig. 2. The piece D is fastened on the bolt an inch or two from the surface of the door to permit placing a spiral spring of medium strength in between as shown in Fig. 3. The opposite end of the bolt may be screwed into the dial, which can be made of wood, or an old safe dial will do. A nail is driven through the outer end of the piece D and the end cut off so that it will pass over the piece B when the dial is turned. When the dial is pulled out slightly and then turned toward the right, the nail will catch on the piece B and open the latch.

Contributed by Geo. Goodbrod, Union, Ore.

Holders in a Convenient Place

When taking hot dishes from the stove, it is very convenient to have holders handy for use. For this purpose I screwed two screw eyes into the ceiling, one in front of the stove directly above the place where the holder should hang, and the other back of the stove and out of the way. I next ran a strong cord through the two eyes. To one end of the cord I attached a weight made of a clean lump of coal. The cord is just long enough to let the weight hang a few inches above the floor and pass through both screw eyes. I fastened a small ring to the other end to keep the cord from slipping back by the pull of the weight. I then fastened two pieces of string to the ring at the end of the cord and attached an iron holder to the end of each string. The strings should be just long enough to keep the holders just over the stove where they are always ready for use, as the weight always draws them back to place.

Contributed by R. S. Merrill, Syracuse, New York.

Box with Hinges and Lock.

The things required to make this trick are a heavy packing box with cover, one pair of special hinges, one or two hasps for as many padlocks and a small buttonhook, says the Sphinx. The hinges must be the kind for attaching inside of the box. If ordinary butts are used, the cover of the box must be cut as much short as the thickness of the end board. The hinges should have pins that will slip easily through the parts.

Before entering the box the performer conceals the buttonhook on his person, and as soon as the cover is closed and locked, and the box placed in a cabinet or behind a screen, he pushes the pin or bolt of the hinge out far enough to engage the knob end with the buttonhook which is used to pull the pin from the hinge. Both hinges are treated in this manner and the cover pushed up, allowing the performer to get out and unlock the padlocks with a duplicate key. The bolts are replaced in the hinges, the box locked and the performer steps out in view.

When sifting flour in an ordinary sieve I hasten the process and avoid the disagreeable necessity of keeping my hands in the flour by taking the top from a small tin lard can and placing it on top of the flour with its sharp edges down. When the sieve is shaken, the can top will round up the flour and press it through quickly.

Contributed by L. Alberta Norrell, Augusta, Ga.

An automobile horn with the bulb and reed detached makes a good funnel. It must be thoroughly cleaned and dried after using as a funnel.

Manner of Forming the Plates

To protect the corners of blotting pads such as will be found on almost every writing desk, proceed as follows:

First, make a design of a size proportionate to the size of the pad and make a right-angled triangle, as shown in Fig. 1, on drawing paper. Leave a small margin all around the edge and then place some decorative form therein. Make allowance for flaps on two sides, as shown, which may later be turned back and folded under when the metal is worked. It should be noted that the corners of the design are to be clipped slightly. Also note the slight overrun at the top with the resulting V-shaped indentation.

To make a design similar to the one shown, draw one-half of it, then fold along the center line and rub the back of the paper with a knife handle or some other hard, smooth surface, and the other half of the design will be traced on the second side. With the metal shears, cut out four pieces of copper or brass of No. 22 gauge and with carbon paper trace the shape and decorative design on the metal. Then cut out the outline and file the edges smooth.

Cover the metal over with two coats of black asphaltum varnish, allowing each coat time to dry. Cover the back and all the face except the white background. Immerse in a solution of 3 parts water, 1 part nitric acid and 1 part sulphuric acid. When the metal has been etched to the desired depth, about 1-32 of an inch, remove it and clean off the asphaltum with turpentine. Use a stick with a rag tied on the end for this purpose so as to keep the solution off the hands and clothes. The four pieces should be worked at the same time, one for each corner.

It remains to bend the flaps. Place the piece in a vise, as shown in Fig. 2, and bend the flap sharply to a right angle. Next place a piece of metal of a thickness equal to that of the blotter pad at the bend and with the mallet bring the flap down parallel to the face of the corner piece, Fig. 3. If the measuring has been done properly, the flaps ought to meet snugly at the corner. If they do not, it may be necessary to bend them back and either remove some metal with the shears or to work the metal over farther. All the edges should be left smooth, a metal file and emery paper being used for this purpose.

If a touch of color is desired, it may be had by filling the etched parts with enamel tinted by the addition of oil colors, such as are used for enameling bathtubs. After this has dried, smooth it off with pumice stone and water. To keep the metal from tarnishing, cover it with banana-oil lacquer.

The following hints will be found useful when boring holes in cork. In boring through rubber corks, a little household ammonia applied to the bit enables one to make a much smoother hole and one that is nearly the same size at both openings. The common cork, if rolled under the shoe sole, can be punctured easily and a hole can be bored straighter. The boring is made easier by boiling the cork, and this operation insures a hole that will he the desired size and remain the size of the punch or bit used.

Arc in a Large Can

A practical and easily constructed self-lighting arc searchlight can be made in the following manner: Procure a large can, about 6 in. in diameter, and cut three holes in its side about 2 in. from the back end, and in the positions shown in the sketch. Two of the holes are cut large enough to hold a short section of a garden hose tightly, as shown at AA. A piece of porcelain tube, B, used for insulation, is fitted tightly in the third hole. The hose insulation A should hold the carbon F rigidly, while the carbon E should rest loosely in its insulation.

The inner end of the carbon E is supported by a piece of No. 25 German-silver wire, C, which is about 6 in. long. This wire runs through the porcelain tube to the binding post D. The binding post is fastened to a wood plug in the end of the tube. The tube B is adjusted so that the end of the carbon E is pressing against the carbon F. The electric wires are connected to the carbon F and the binding post D. A resistance, R, should be in the line.

The current, in passing through the lamp, heats the strip of German-silver wire, causing it to expand. This expansion lowers the end of the carbon E, separating the points of the two carbons and thus providing a space between them for the formation of an arc. When the current is turned off, the German-silver wire contracts and draws the two carbon ends together ready for lighting again. The feed can be adjusted by sliding the carbon F through its insulation.

A resistance for the arc may be made by running the current through a water rheostat or through 15 ft. of No. 25 gauge German-silver wire.

Contributed by R. H. Galbreath, Denver, Colo.

Take an ordinary collapsible drinking cup and place a cake of shaving soap in the bottom ring. This will provide a shaving mug always ready for the traveler and one that will occupy very little space in the grip.

Made from Barrel Staves

Secure four light barrel staves and sandpaper the outside smooth. Take two old shoes that are extra large and cut off the tops and heels so as to leave only the toe covering fastened to the sole. Purchase two long book straps, cut them in two in the middle and fasten the ends on the toe covering, as shown in Fig. 1. The straps are used to attach the snowshoe to the regular shoe. When buckling up the straps be sure to leave them loose enough for the foot to work freely, Fig. 2. Fasten the barrel staves in pairs, leaving a space of 4 in. between them as shown in Fig. 3, with thin strips of wood. Nail the old shoe soles to crosspieces placed one-third of the way from one end as shown.

Contributed by David Brown, Kansas City, Mo.

Bell and Battery in a Box

Watching a fish line set in a hole cut in the ice on a cold day is very disagreeable, and the usual method is to have some kind of a device to signal the fisherman when a fish is hooked. The "tip ups" and the "jumping jacks" serve their purpose nicely, but a more elaborate device is the electric signal. A complete electric outfit can be installed in a box and carried as conveniently as tackle.

An ordinary electric bell, A, Fig. 1, having a gong 2-1/2 in. in diameter, and a pocket battery, B are mounted on the bottom of the box. The electric connection to the bell is plainly shown. Two strips of brass, C, are mounted on the outside of the box. The brass strips are shaped in such a way as to form a circuit when the ends are pulled together. The box is opened and set on the ice near the fishing hole. The fish line is hung over a round stick placed across the hole and then tied to the inside strip of brass. When the fish is hooked the line will pull the brass points into contact and close the electric circuit.

A floor polisher is something that one does not use but two or three times a year. Manufactured polishers come in two sizes, one weighing 15 lb., which is the right weight for family use, and one weighing 25 lb.

A polisher can be made at home that will do the work just as well. Procure a wooden box such as cocoa tins or starch packages are shipped in and stretch several thicknesses of flannel or carpet over the bottom, allowing the edges to extend well up the sides, and tack smoothly. Make a handle of two stout strips of wood, 36 in. long, by joining their upper ends to a shorter crosspiece and nail it to the box. Place three paving bricks inside of the box, and the polisher will weigh about 16 lb., just the right weight for a woman to use. The polisher is used by rubbing with the grain of the wood.

Contributed by Katharine D. Morse, Syracuse, N. Y.

Stages in Tying a Bag

In tying the ordinary paper bag, the string can be placed in the paper in such a way that it will form a handle to carry the package, and also prevent any leakage of the contents. The bag must be long enough for the end to fold over as shown in Fig. 1. The folds are made over the string, as in Fig. 2. The string is then tied, Fig. 3, to form a handle, Fig. 4.

Contributed by James M. Kane, Doylestown, Pa.

Warping the Aeroplane Wings

On one of my model aeroplanes I placed an equilibrator to keep it balanced. The device was attached to a crosspiece fastened just below the propeller between the main frame uprights. A stick was made to swing on a bolt in the center of the crosspiece to which was attached a weight at the lower end and two lines connecting the ends of the planes at the upper end. These are shown in Fig. 1. When the aeroplane tips, as shown in Fig. 2, the weight draws the lines to warp the plane so it will right itself automatically.

Contributed by Louis J. Day, Floral Park, N. Y.

Small glass ornaments for Christmas tree decorations are very easily broken on the line shown in the sketch. These can be easily repaired by inserting in the neck a piece of match, toothpick or splinter of wood and tying the hanging string to it.

Frame Made of a Rod

A scroll saw, if once used, becomes indispensable in any home carpenter chest, yet it is safe to say that not one in ten contains it. A scroll saw is much more useful than a keyhole saw for sawing small and irregular holes, and many fancy knick-knacks, such as brackets, bookracks and shelves can be made with one.

A simple yet serviceable scroll saw frame can be made from a piece of cold-rolled steel rod, 3/32 or 1/4 in. in diameter, two 1/8-in. machine screws, four washers and four square nuts. The rod should be 36 or 38 in. long, bent as shown in Fig. 1. Place one washer on each screw and put the screws through the eyelets, AA, then place other washers on and fasten in place by screwing one nut on each screw, clamping the washers against the frame as tightly as possible. The saw, which can be purchased at a local hardware store, is fastened between the clamping nut and another nut as shown in Fig. 2.

If two wing nuts having the same number and size of threads are available, use them in place of the outside nuts. They are easier to turn when inserting a saw blade in a hole or when removing broken blades.

Contributed by W. A. Scranton, Detroit, Michigan.

Watch Fob

The fixtures for the watch fob shown—half size—may be made of either brass, copper, or silver. Silver is the most desirable but, of course, the most expensive. The buckle is to be purchased. The connection is to be of leather of a color to harmonize with that of the fixtures. The body of the fob may be of leather of suitable color or of silk. Of the leathers, green and browns are the most popular, though almost any color may be obtained.

Make full size drawings of the outline and design of the fixtures. With carbon paper trace these on the metal. Pierce the metal of the parts that are to be removed with a small hand drill to make a place for the leather or silk. With a small metal saw cut out these parts and smooth up the edges, rounding them slightly so they will not cut the leather or silk. Next cut out the outlines with the metal shears. File these edges, rounding and smoothing with emery paper. The best way of handling the decorative design is to etch it and, if copper or brass, treat it with color.

For etching, first cover the metal with black asphaltum varnish, on the back and all the parts that are not to be touched with the acid. In the design shown, the unshaded parts should not be etched and should, therefore, be covered the same as the back. Apply two coats, allowing each time to dry, after which immerse the metal in a solution prepared as follows: 3 parts water, 1 part nitric acid, 1 part sulphuric acid. Allow the metal to remain in this until the acid has eaten to a depth of 1/32 in., then remove it and clean in a turpentine bath, using a swab and an old stiff brush. The amount of time required to do the etching will depend upon the strength of the liquid, as well as the depth of etching desired.

For coloring silver, as well as brass and copper, cover the metal with a solution of the following: 1/2 pt. of water in which dissolve, after breaking up, five cents worth of sulphureted potassium. Put a teaspoonful of this into a tin with 2 qt. of water. Polish a piece of scrap metal and dip it in the solution. If it colors the metal red, it has the correct strength. Drying will cause this to change to purple. Rub off the highlights, leaving them the natural color of the metal and apply a coat of banana-oil lacquer.

Parts of the Top

All parts of the top are of wood and they are simple to make. The handle is a piece of pine, 5-1/4 in. long, 1-1/4 in. wide and 3/4 in. thick. A handle, 3/4 in. in diameter, is formed on one end, allowing only 1-1/4 in. of the other end to remain rectangular in shape. Bore a 3/4-in. hole in this end for the top. A 1/16-in. hole is bored in the edge to enter the large hole as shown. The top can be cut from a broom handle or a round stick of hardwood.

To spin the top, take a piece of stout cord about 2 ft. long, pass one end through the 1/16-in. hole and wind it on the small part of the top in the usual way, starting at the bottom and winding upward. When the shank is covered, set the top in the 3/4-in. hole. Take hold of the handle with the left hand and the end of the cord with the right hand, give a good quick pull on the cord and the top will jump clear of the handle and spin vigorously.

Contributed by J.F. Tholl, Ypsilanti, Michigan.

Pockets for Thread

A detachable pocket for holding thread when sewing is shown herewith. The dimensions may be varied to admit any number or size of spools. Each pocket is made to take a certain size spool, the end of the thread being run through the cloth front for obtaining the length for threading a needle. This will keep the thread from becoming tangled and enable it always to be readily drawn out to the required length.

Contributed by Miss L. Alberta Norrell, Augusta, Ga.

Beat up the whites of three eggs carefully and use a piece of flannel to rub it well into the leather which will become clean and lustrous. For black leathers, some lampblack may be added and the mixture applied in the same way.

Baking Pan without Sides

When making cookies, tarts or similar pastry, the housewife often wishes for something by which to lift the baked articles from the pan. The baking tray or pan shown in the sketch not only protects the hands from burns but allows the baked articles easily to slip from its surface. The pan is made from a piece of sheet iron slightly larger than the baking space desired. Each end of the metal is cut so that a part may be turned up and into a roll to make handles for the pan.

A wire or small rod is placed between the handles as shown. This wire is fastened at each end and a loop made in the center. The pan can be removed from the oven by placing a stick through the loop and lifting it out without placing the hands inside the hot oven. The baking surface, having no sides, permits the baked articles to be slid off at each side with a knife or fork.

A. A. Houghton, Northville, Mich.

A very simple and effective device for holding a broom when it is not in use is shown in the sketch. It is made of heavy wire and fastened to the wall with two screw eyes, the eyes forming bearings for the wire. The small turn on the end of the straight part is to hold the hook out far enough from the wall to make it easy to place the broom in the hook. The weight of the broom keeps it in position.

Contributed by Irl Hicks, Centralia, Mo.

A string for drawing electric wires into bent fixtures can be easily inserted by rolling it into a small ball and blowing it through while holding one end.

Darkroom Lantern

Procure an ordinary 2-qt. glass fruit jar, break out the porcelain lining in the cover and cut a hole through the metal, just large enough to fit over the socket of an incandescent electric globe, then solder cover and socket together, says Studio Light. Line the inside of the jar with two thicknesses of good orange post office paper. The best lamp for the purpose is an 8-candlepower showcase lamp, the same as shown in the illustration. Screw the lamp into the socket and screw the cover onto the jar, and you have a safe light of excellent illuminating power.

When you desire to work by white light, two turns will remove the jar.

If developing papers are being worked, obtain a second jar and line with light orange paper, screw into the cover fastened to the lamp and you have a safe and pleasant light for loading and development. By attaching sufficient cord to the lamp, it can be moved to any part of the darkroom, and you have three lamps at a trifling cost.

Many housekeepers do not know that there is a simple way to prevent potatoes from burning and sticking to the bottom of the pot. An inverted pie pan placed in the bottom of the pot avoids scorching potatoes. The water and empty space beneath the pan saves the potatoes. This also makes the work of cleaning pots easier as no adhering parts of potatoes are left to be scoured out.

Folding Clothes Rack

A clothes-drying rack that has many good features can be made as shown in the illustration. When the rack is closed it will fit into a very small space and one or more wings can be used at a time as the occasion or space permits, and not tip over. The rack can be made of any hard wood and the material list is as follows:

1 Center post. 1-1/4 in. square by 62 in.
4 Braces. 1-1/4 in. square by 12 in.
16 Horizontal bars. 1 by 1-1/4 by 24 in.
4 Vertical pieces. 1/4 by 1 by 65 in.

Attach the four braces for the feet with finishing nails after applying a good coat of glue.

The horizontal bars are fastened to the vertical pieces with rivets using washers on both sides. The holes are bored a little large so as to make a slightly loose joint. The other ends of the bars are fastened to the center post with round head screws. They are fastened, as shown in the cross-section sketch, so it can be folded up.

Contributed by Herman Fosel, Janesville, Wis.

A Shower Bath That Costs Less Than One Dollar to Make

While in the country during vacation time, I missed my daily bath and devised a shower bath that gave complete satisfaction. The back porch was enclosed with sheeting for the room, and the apparatus consisted of a galvanized-iron pail with a short nipple soldered in the center of the bottom and fitted with a valve and sprinkler. The whole, after filling the pail with water, was raised above one's head with a rope run over a pulley fastened to the roof of the porch, and a tub was used on the floor to catch the water. A knot should be tied in the rope at the right place, to keep it from running out of the pulley while the pail is lowered to be filled with water, and a loop made in the end, which is placed over a screw hook turned into the wall. If the loop is tied at the proper place, the pail will be raised to the right height for the person taking the shower bath.

The water will run from 10 to 15 minutes. The addition of some hot water will make a splendid shower bath.

Contributed by Dr. C. H. Rosenthal, Cincinnati, O.

As I needed several small sprocket wheels and had none on hand, I made them quickly without other expense than the time required, from scrap material. Several old hubs with the proper size bore were secured. These were put on an arbor and turned to the size of the bottom of the teeth. Hole were drilled and tapped to correspond to the number of teeth required and old stud bolts turned into them. The wheels were again placed on the arbor and the studs turned to the required size. After rounding the ends of the studs, the sprockets were ready for use and gave perfect satisfaction.

Contributed by Charles Stem, Phillipsburg, New York.

FIG. 1
FIG. 2
Closet for Holding Pot Covers

The sides of the cover closet are cut as shown in Fig. 1 and shelves are nailed between them at a slight angle. No dimensions are given as the space and the sizes of the covers are not always the same. The back is covered with thin boards placed vertically. The front can be covered with a curtain or a paneled door as shown.

Contributed by Gilbert A. Wehr, Baltimore, Md.

Bottle in Stand

Some cooks find it a very difficult matter to prepare salad dressing, principally mayonnaise dressing, as the constant stirring and pouring of oil and liquids are required in the operation. The simple homemade device shown in the accompanying sketch greatly assists in this work. It consists of a stand to hold a bottle, the mouth of which rests against a small gate directly in the rear of the attached tin trough. The weight of the bottle and the contents against the gate serves as a check or stopper. If the gate is raised slightly, it will permit a continuous flow of liquid of the desired amount.

In using developing papers, either for contact printing or enlargements, you are, by all rules of the game, entitled to a certain number of overexposed prints, says a correspondent of Camera Craft. But there is no reason why you should lose either the paper or the time and trouble expended in making these prints. By using the following method, you can turn these very dark prints into good ones.

First: these overexposed prints must be fully developed. Do not try to save them by rushing them out of the developer into the short-stop or fixing bath. The results will be poor, and, if you try to tone them afterward, the color will be an undesirable, sickly one. Develop them into strong prints, thoroughly fix, and wash until you are sure all hypo is removed. In my own practice, I carry out this part of the work thoroughly, then dry the prints and lay aside these dark ones until there is an accumulation of a dozen or more, doing this to avoid too frequent use of the very poisonous bleaching solution. The bleacher is made up as follows and should be plainly marked "Poison."

Place the dry print, without previous wetting, in this solution. It will bleach slowly and evenly, but, when it starts to bleach, transfer it to a tray of water, where it will continue to bleach. When the desired reduction has taken place, stop the action at once by immersing the print in a 10-per-cent solution of borax. The prints may be allowed to remain in this last solution until they are finished. A good final washing completes the process. This washing must be thorough and a sponge or a tuft of cotton used to clean the surface of the print.

With a little practice, this method of saving prints that are too dark becomes easy and certain. The prints are lightened and at the same time improved in tone, being made blue-black with a delicate and pleasing quality that will tempt you to purposely overexpose some of your prints in order to tone them by this method for certain effects. The process is particularly valuable to the worker in large sizes, as it provides a means of making quite a saving of paper that would otherwise be thrown away.

Stand Attached to Table

An ordinary ironing board is cut square on the large end and a slot cut 1-1/2 in. wide and 4 in. long to admit the angle support. The support is placed against the table and the board is pressed down against the outer notch which jams against the table, thus holding the board rigid and in such a position as to give free access for ironing dresses, etc.

Contributed by T. L. Gray, San Francisco, Cal.

Fig 3 Paper Corners for Blotter Pads

Procure four sheets of blotting paper, preferably the colored kind, as it will appear clean much longer than the white. The size of the pad depends on the size of the blotting paper.

Fold four pieces of ordinary wrapping paper, 5 by 15 in. in size, three times, to make it 5 by 5 in. Fold each one from corner to corner as shown in Fig. 1 and again as in Fig. 2. Paste the last fold together and the corner holders are complete. Put one on each corner of the blotting paper. They can be fastened with a small brass paper fastener put through the top of the holder. The blotting paper can be easily changed by removing the holders and fasteners. Corners complete are shown in Fig. 3.

Contributed by J. Wilson Aldred Toronto, Canada.

Wires Attached to a Lavatory

A very handy article is an attachment on wash basins or lavatories for holding the sleeves back while washing the hands. It is very annoying to have the sleeves continually slip down and become wet or soiled. The simple device shown herewith can be made with bent wires or hooks and attached in such a way that it can be dropped out of the way when not in use.

Contributed by L. J. Monahan, Oshkosh, Wisconsin.

A pencil eraser will remove the tarnish from nickel plate, and the ink eraser will remove the rust from drawing instruments.

Fig. 1       Fig. 2
The Pattern and the Finished Bookmark

Secure a piece of brass of No. 20 gauge, having a width of 2-1/4 in. and a length of 5 in. Make a design similar to that shown, the head of which is 2 in. wide, the shaft 1 in. wide below the head and the extreme length 4-1/2 in. Make one-half of the design, as shown in Fig. 1, freehand, then trace the other half in the usual way, after folding along the center line. Trace the design on the metal, using carbon paper, which gives the outline of the design Fig. 2.

Drilling and Sawing the Metal

With the metal shears, cut out the outline as indicated by the drawing. With files, smooth off any roughness and form the edge so that it shall be nicely rounded.

The parts of the design in heavy color may be treated in several ways. A very satisfactory treatment is obtained by etching, then coloring. Clean the metal thoroughly with pumice stone and water or with alcohol before the design is applied. Cover all the metal that is not to be lowered with a thick coating of asphaltum. Allow this to dry, then put on a second coat. After this has dried, thoroughly immerse the metal in a solution composed as follows: 3 parts water, 1 part sulphuric acid, 1 part nitric acid.

Allow the metal to remain in this solution until the exposed part has been eaten about 1/32 in. deep, then remove it and clean off the asphaltum, using turpentine. Do not put the hands in the solution, but use a swab on a stick.

For coloring olive green, use 2 parts water to 1 part permuriate of iron. Apply with a small brush.

The lines at A and B will need to be cut, using a small metal saw. Pierce a hole with a small drill, Fig. 3, large enough to receive the saw and cut along the lines as in Fig. 4. A piece of wood with a V-shaped notch which is fastened firmly to the bench forms the best place in which to do such sawing. The teeth of the saw should be so placed that the sawing will be done on the downward stroke. The metal must be held firmly, and the saw allowed time to make its cut, being held perpendicular to the work.

After the sawing, smooth the edges of the metal with a small file and emery paper. The metal clip may be bent outward to do this part of the work.

The cover from a cheesebox can be converted into a tea tray that is very dainty for the piazza, or for serving an invalid's breakfast.

First sandpaper the wood until it is smooth, then stain it a mahogany color. The mahogany stain can be obtained ready prepared. After the stain has dried, attach brass handles, which can be obtained for a small sum at an upholsterer's shop. A round embroidered doily in the bottom adds to the appearance of the tray.

Contributed by Katharine D. Morse, Syracuse, New York.

Drill a 1/2-in. hole through a block of pine or other soft wood 2 in. thick. Tack over one end of the hole a piece of pasteboard in which seven coarse sewing-machine needles have been inserted. The needles should be close together and pushed through the pasteboard until the points show. The hole is then filled with melted babbitt metal. When this is cold, the block is split and the pasteboard removed. This tool makes neat pierced work and in making brass shades, it does the work rapidly.

Contributed by H. Carl Cramer, East Hartford, Conn.

Knife Attached to the Board

Cooks can slice, chop or mince vegetables and various other food rapidly by placing the little device, as shown, on a chopping board. Ii is an ordinary staple, driven in just far enough to allow a space for the end of an ordinary pointed kitchen knife to fit in it. The staple is driven in the edge of the chopping board. The knife can be raised and lowered with one hand, as the material is passed under the blade with the other. Great pressure can be applied and the knife will not slip.

Contributed by M. M. Burnett, Richmond, Cal.

Sew straps to the sides of mattresses and they can be handled much easier.

Round Stick In a Spool

The home workshop can be supplied with a carpenter's gauge without any expense' by the use of a large spool and a round stick of wood. The stick should be dressed to fit the hole in the spool snugly and a small brad driven through one end so that the point will protrude about 1/16 in.

The adjustment of the gauge is secured by driving the stick in the hole in the direction desired. A better way and one that will make the adjusting easy is to file the point end of a screw eye flat and use it as a set screw through a hole in the side of the spool.

Board or Wall Iron Rest

The iron rest and wall hanger shown in the sketch is made of sheet iron. The upturned edges of the metal are bent to fit the sloping sides of the iron. The holder and iron can be moved at the same time.

Contributed by W. A. Jaquythe, Richmond, Cal.

When groceries are delivered, save the paper bags and use them for staring bread and cakes. Tie the neck of the bag with a string and it will keep the contents fresh and clean.

Contributed by Mrs. L. H. Atwell, Kissimmee, Florida.

If a little chalk is rubbed on a file before filing steel, it will keep the chips from sticking in the cuts on the file and scratching the work.

Details of the Turbine

Procure some brass, about 3/16 in. thick and 4 in. square; 53 steel pens, not over 1/4 in. in width at the shank; two enameled, or tin, saucers or pans, having a diameter on the inside part of about 4-1/2 in.; two stopcocks with 1/8 in. holes; one shaft; some pieces of brass, 1/4 in. thick, and several 1/8-in. machine screws.

Lay out two circles on the 3/16-in. brass, one having a diameter of 3-1/2 in. and the other with a diameter of 2-3/4 in. The outside circle is the size of the finished brass wheel, while the inside circle indicates the depth to which the slots are to be cut. Mark the point where a hole is to be drilled for the shaft, also locate the drill holes, as shown at A, Fig. 1. After the shaft hole and the holes A are drilled in the disk, it can be used as template for drilling the side plates C.

The rim of the disk is divided into 53 equal parts and radial lines drawn from rim to line B, indicating the depth of the slots. Slots are cut in the disk with a hacksaw on the radial lines. A small vise is convenient for holding the disk while cutting the slots. When cutting the disk out of the rough brass, sufficient margin should be left for filing to the true line. The slots should be left in their rough state as they have a better hold on the pens which are used for the blades. The pens are inserted in the slots and made quite secure by forcing ordinary pins on the inside of the pens and breaking them off at the rim, as shown in Fig. 4.

When the pens are all fastened two pieces of metal are provided, each about 1 in. in diameter and 1/32 in. thick, with a 3/8-in. hole in the center, for filling pieces which are first placed around the shaft hole between the disk and side plates C, Fig. 1. The side plates are then secured with some of the 1/8-in. machine screws, using two nuts on each screw. The nuts should be on the side opposite the inlet valves. The shaft hole may also be filed square, a square shaft used, and the ends filed round for the bearings.

The casing for the disk is made of two enameled-iron saucers, Fig. 2, bolted together with a thin piece of asbestos between them to make a tight joint. A 3/4-in. hole is cut near the edge of one of the saucers for the exhaust. If it is desired to carry the exhaust beyond the casing, a thin pipe can be inserted 1/4 in. into the hole. Holes are drilled through the pipe on both inside and outside of the casing, and pins inserted, as shown in Fig. 5. Solder is run around the outside pin to keep the steam from escaping. At the lowest point of the saucer or casing a 1/8-in. hole is drilled to run off the water. A wood plug will answer for a stopcock.

If metal dishes, shaped from thick material with a good coating of tin, can be procured, it will be much easier to construct the casing than if enameled ware is used. The holes can be easily drilled and the parts fitted together closely. All seams and surfaces around fittings can be soldered.

Nozzles are made of two stopcocks having a 1/8-in. hole. These are connected to a 3/8-in. supply pipe. The nozzles should be set at an angle of 20 deg. with the face of the disk. The nozzle or stopcock will give better results if the discharge end is filed parallel to the face of the disk when at an angle of 20 deg. There should be a space of 1/16 in. between the nozzle and the blades to allow for sufficient play, Fig. 3.

The bearings are made of 1/4-in. brass and bolted to the casing, as shown, with 1/8-in. machine screws and nuts. Two nuts should be placed on each screw. The pulley is made by sliding a piece of steel pipe on the engine shaft and fastening it with machine screws and nuts as shown in Fig. 6. If the shaft is square, lead should be run into the segments.

The driven shaft should have a long bearing. The pulley on this shaft is made of pieces of wood nailed together, and its circumference cut out with a scroll saw. Flanges are screwed to the pulley and fastened to the shaft as shown in Fig. 7.

The bearings are made of oak blocks lined with heavy tin or sheet iron for the running surface. Motion is transmitted from the engine to the large pulley by a thin but very good leather belt.

Brass Key on a Wood Base

A simple and easily constructed telegraph key may be made in the following manner: Procure a piece of sheet brass, about 1/32 in. thick, and cut out a strip 3-1/2 in. long by 3/4 in. wide. Bend as shown in Fig. 1 and drill a hole for the knob in one end and a hole for a screw in the other. Procure a small wood knob and fasten it in place with a small screw. Cut a strip of the same brass 2-3/4 in. long and 5/16 in. wide and bend as shown in Fig. 2. Drill two holes in the feet for screws to fasten it to the base, and one hole in the top part for a machine screw, and solder a small nut on the under side of the metal over the hole.

Mount both pieces on a base 4-1/4 by 2-3/4 by 1/4 in., as in Fig. 3, and where the screw of the knob strikes the base when pressed down, put in a screw or brass-headed tack for a contact. Fasten the parts down with small brass wood-screws and solder the connections beneath the base. Binding posts from an old battery cell are used on the end of the base. The screw on top of the arch is used to adjust the key for a long or short stroke.

Contributed by S. V. Cooke, Hamilton, Canada.

Camps and suburban homes located where ice is hard to get can be provided with a cooling arrangement herein described that will make a good substitute for the icebox. A barrel is sunk in the ground in a shady place, allowing plenty of space about the outside to fill in with gravel. A quantity of small stones and sand is first put in wet. A box is placed in the hole over the top of the barrel and filled in with clay or earth well tamped. The porous condition of the gravel drains the surplus water after a rain.

The end of the barrel is fitted with a light cover and a heavy door hinged to the box. A small portion of damp sand is sprinkled on the bottom of the barrel. The covers should be left open occasionally to prevent mold and to remove any bad air that may have collected from the contents.

Contributed by F. Smith, La Salle, Ill.

Secure a cheese box about 12 in. high and 15 in. or more in diameter. It will pay you to be careful in selecting this box. Be sure to have the cover. Score the wood deeply with a carpenter's gauge inside and out 3-1/2 in. from the top of the box. With repeated scoring the wood will be almost cut through or in shape to finish the cut with a knife. Now you will have the box in two pieces. The lower part, 8-1/2 in. deep over all, we will call the basket, and the smaller part will be known as the tray.

Remove the band from the cover and cut the boards to fit in the tray flush with the lower edge, to make the bottom. Fasten with 3/4-in brads. The kind of wood used in making these boxes cracks easily and leaves a rough surface which should be well sandpapered.

The four legs are each 3/4-in. square and 30-1/2 in. long. The tops should be beveled to keep them from splintering at the edges. With a string or tape measure, find the circumference of the tray or basket and divide this into four equal parts, arranging the lap seam on both to come midway between two of the marks. When assembling, make these seams come between the two back legs.

The tray is placed 1-1/4 in. from the top end and the basket 6-3/4 in. from the bottom end of the legs. Notch the legs at the lower point about 1/8 in. deep and 1-1/4 in. wide to receive the band at the lower end of the basket. Fasten with 3/4-in. screws, using four to each leg, three of which are in the basket. Insert the screws from the inside of the box into the legs.

Stain the wood before putting in the lining. If all the parts are well sandpapered, the wood will take the stain nicely: Three yards of cretonne will make a very attractive lining. Cut two sheets of cardboard to fit in the bottom of the tray and basket. Cover them with the cretonne, sewing on the back side. Cut four strips for the sides from the width of the goods 5-1/2 in. wide and four strips 10 in. wide. Sew them end to end and turn down one edge to a depth of 1 in. and gather it at that point,—also the lower edge when necessary. Sew on to the covered cardboards. Fasten them to the sides of the tray and basket with the smallest upholsterers' tacks. The product of your labor will be a very neat and useful piece of furniture.

Contributed by Stanley H. Packard, Boston, Mass.

Paper Aeroplanes in Draft

A novel and attractive aeroplane window display can be easily made in the following manner: Each aeroplane is cut from folded paper, as shown in the sketch, and the wings bent out on the dotted lines. The folded part in the center is pasted together. Each aeroplane is fastened with a small thread from the point A as shown. A figure of an airman can be pasted to each aeroplane. One or more of the aeroplanes can be fastened in the blast of an electric fan and kept in flight the same as a kite. The fan can be concealed to make the display more real. When making the display, have the background of such a color as to conceal the small threads holding the aeroplanes.

Contributed by Frederick Hennighausen, Baltimore, Md.

Fig.2 Fig.3 The Stone Chipped into Shape

If you live where flints abound, possess the requisite patience and the knack of making things, you can, with the crudest of tools and a little practice, chip out as good arrowheads as any painted savage that ever drew a bow. Select a piece of straight-grained flint as near the desired shape as possible. It may be both longer and wider than the finished arrow but it should not be any thicker. The side, edge and end views of a suitable fragment are shown in Fig. 1. Hold the piece with one edge or end resting on a block of wood and strike the upper edge lightly with a hammer, a small boulder or anything that comes handy until the piece assumes the shape shown in Fig. 2.

The characteristic notches shown in the completed arrow, Fig. 3, are chipped out by striking the piece lightly at the required points with the edge of an old hatchet or a heavy flint held at right angles to the edge of the arrow. These heads can be made so that they cannot be distinguished from the real Indian arrowheads.

Contributed by B. Orlando Taylor, Cross Timbers, Mo.

Handle on Cover

A stamp pad is a desk necessity and the cleanliness of one depends on keeping it closed when it is not in use. The opening and closing of a pad requires both hands and consequently the closing of a pad is often neglected in order to avoid soiling the fingers. This trouble can be avoided if the pad is fitted with a small handle as shown in the sketch. Take the ordinary pad and work the hinge until it opens freely. If necessary apply a little oil and spread the flanges of the cover slightly.

Saw off the top of a common wood clothespin just above the slot, saving all the solid part. Fasten this to the cover near the back side in an upright position with a screw. A tap on the front side of the pin will turn it over backward until the head rests on the desk thus bringing the cover up in the upright position. When through using the pad, a slight tap on the back side of the cover will turn it down in place.

Contributed by H. L. Crockett, Gloversville, N. Y.

Finished Kennel

Concrete Forms

The kennel shown in the illustration is large enough for the usual size of dog. It is cleanly, healthful and more ornamental than the average kennel. This mission style would be in keeping with the now popular mission and semi-mission style home, and, with slight modifications, it could be made to conform with the ever beautiful colonial home. It is not difficult to build and will keep in good shape for many years.

The dimensions and the manner of making the forms for the concrete, and the location for the bolts to hold the plate and rafters, are shown in the diagram.

Contributed by Edith E. Lane, El Paso, Texas.

Photograph in the Shell

Split an English walnut in the center, remove the contents, and scrape out the rough parts. Make an oval opening by filing or grinding. If a file is used, it should be new and sharp. After this is done, take a small half round file and smooth the edges into shape and good form.

The photograph print should be quite small—less than 1/2 in. across the face. Trim the print to a size a little larger than the opening in the shell, and secure it in place with glue or paste. It may be well to fill the shell with cotton. Mount the shell on a small card with glue, or if desired, a mount of different shape can be made of burnt woodwork.

Contributed by C. S. Bourne, Lowell, Mass.

Spoon Holder

In making marmalade and jellies the ingredients must be stirred from time to time as the cooking proceeds. After stirring, some of the mixture always remains on the spoon. Cooks often lay the spoon on a plate or stand it against the cooking utensil with the handle down. Both of these methods are wasteful. The accompanying illustration shows a device made of sheet copper to hold the spoon so that the drippings will return to the cooking utensil. The copper is not hard to bend and it can be shaped so that the device can be used on any pot or kettle.

Contributed by Edwin Marshall, Oak Park, Ill.

Some time ago I received two gramophone records that were cracked in shipment but the parts were held together with the paper label. As these were single-faced disk records, I used the following method to stick them together: I covered the back of one with shellac and laid the two back to back centering the holes with the crack in one running at right angles to the crack in the other. These were placed on a flat surface and a weight set on them. After several hours' drying, I cleaned the surplus shellac out of the holes and played them.

As the needle passed over the cracks the noise was hardly audible. These records have been played for a year and they sound almost as good as new.

Contributed by Marion P. Wheeler, Greenleaf, Oregon.

An amateur mechanic who had been much annoyed by the insects which were attracted to his electric lights found a solution in the pneumatic moth trap described in a recent issue of Popular Mechanics. He fixed a funnel to the end of the intake tube of a vacuum cleaner and hung it under a globe. The insects came to the light, circled over the funnel and disappeared. He captured several pounds in a few hours.

Contributed by Geo. F. Turl, Canton, Ill.

In filtering a large amount of solution one usually desires some means other than a large funnel and something to make the watching of the process unnecessary. If a considerable quantity of a solution be placed in a large bottle or flask, and a cork with a small hole in it inserted in the mouth, and the apparatus suspended in an inverted position over a small funnel so that the opening of the cork is just below the water level in the funnel, the filtering process goes on continuously with no overflow of the funnel.

As soon as the solution in the funnel is below the cork, air is let into the flask and a small quantity of new solution is let down into the funnel. The process works well and needs no watching, and instead of the filtrate being in a large filter paper, it is on one small piece and can be handled with ease.

Contributed by Loren Ward, Des Moines, Iowa.

Finished Rack

Details of the Rack

The illustration shows a rack for postcards. Those having houses with mission-style furniture can make such a rack of the same material as the desk, table or room furnishings and finish it in the same manner.

The dimensions are given in the detail sketch. The two ends are cut from 1/4-in. material, the bottom being 3/8 in. thick. Only three pieces are required, and as they are simple in design, anyone can cut them out with a saw, plane and pocket knife.

Contributed by Wm. Rosenberg, Worcester, Mass.

A good substitute for a shoe horn is a handkerchief or any piece of cloth used in the following way: Allow part of the handkerchief or cloth to enter the shoe, place the toe of the foot in the shoe so as to hold down the cloth, and by pulling up on the cloth so as to keep it taut around the heel the foot will slide into the shoe just as easily as if a shoe horn were used.

Contributed by Thomas E. Dobbins, Glenbrook, Conn.

In building a photographic dark room, it is necessary to make it perfectly light-tight, the best material to use being matched boards. These boards are tongued and grooved and when put together effectually prevent the entrance of light.

The next important thing to be considered is to make it weather-tight, and as far as the sides are concerned the matched boards will do this also, but it is necessary to cover the roof with felt or water-proof paper.

The best thickness for the boards is 1 in., but for cheapness 3/4 in. will do as well, yet the saving is so little that the 1-in. boards are preferable.

The dark room shown in the accompanying sketch measures 3 ft. 6 in. by 2 ft. 6 in., the height to the eaves being 6 ft. Form the two sides shown in Fig 1, fixing the crosspieces which hold the boards together in such positions that the bottom one will act as a bearer for the floor, and the second one for the developing bench. Both sides can be put together in this way, and both exactly alike. Keep the ends of the crosspieces back from the edges of the boards far enough to allow the end boards to fit in against them.

One of the narrow sides can be formed in the same way, fixing the crosspieces on to correspond, and then these three pieces can be fastened together by screwing the two wide sides on the narrow one.

Lay the floor next, screwing or nailing the boards to the crosspieces, and making the last board come even with the ends of the crosspieces, not even with the boards themselves. The single boards can then be fixed, one on each side of what will be the doorway, by screwing to the floor, and to the outside board of the sides. At the top of the doorway, fix a narrow piece between the side boards, thus leaving a rectangular opening for the door.

The roof boards may next be put on, nailing them to each other at the ridge, and to the sides of the room at the outsides and eaves. They should overhang at the sides and eaves about 2 in., as shown in Figs. 3 and 4.

One of the sides with the crosspieces in place will be as shown in Fig. 2 in section, all the crosspieces and bearers intersecting around the room.

The door is made of the same kind of boards held together with crosspieces, one of which is fastened so as to fit closely to the floor when the door is hinged, and act as a trap for the light. The top crosspiece is also fastened within 1 in. of the top of the door for the same reason.

Light traps are necessary at the sides and top of the door. That at the hinged side can be as shown at A, Fig. 5, the closing side as at B, and the top as at C in the same drawing. These are all in section and are self-explanatory. In hinging the door, three butt hinges should be used so as to keep the joint close.

The fittings of the room are as shown sectionally in Fig. 6, but before fixing these it is best to line the room with heavy, brown wrapping paper, as an additional safeguard against the entrance of light.

The developing bench is 18 in. wide, and in the middle an opening, 9 by 11 in., is cut, below which is fixed the sink. It is shown in detail in Fig. 7, and should be zinc lined.

The zinc should not be cut but folded as shown in Fig. 8, so that it will fit inside the sink. The bench at each side of the sink should be fluted (Fig. 9), so that the water will drain off into the sink. A strip should be fixed along the back of the bench as shown in Figs. 6 and 9, and an arrangement of slats (Fig. 10), hinged to it, so as to drop on the sink as in Fig. 6, and shown to a larger scale in Fig. 11.

Details of the Dark Room

A shelf for bottles and another for plates, etc., can be fixed above the developing bench as at D and E (Fig. 6) and another as F in the same drawing. This latter forms the bottom of the tray rack, which is fixed on as shown in Fig. 13. The divisions of the tray rack are best fitted loosely in grooves formed by fixing strips to the shelves and under the bench and sink as in Fig. 13.

Extra bearing pieces will be wanted for the shelves mentioned above, these being shown in Fig. 14. The window is formed by cutting an opening in the side opposite the door, and fixing in it a square of white glass with strips of wood on the inside and putty on the outside, as in Fig. 15. A ruby glass is framed as shown at G, Fig. 16, and arranged to slide to and fro in the grooved runners H, which makes it possible to have white light, as at I, or red light as at K, Fig. 16. The white glass with runners in position is shown at L in the same drawing, but not the red glass and frame. Ventilation is arranged for by boring a series of holes near the floor, as at M, Fig. 6, and near the roof as at N in the same drawing, and trapping the light without stopping the passage of air, as shown in the sections, Fig. 17.

The finish of the roof at the gables is shown in Fig. 18, the strip under the boards holding the felt in position when folded under, and the same is true of the roll at the top of the roof in Fig. 19.

The house will be much strengthened if strips, as shown in Fig. 20, are fastened in the corners inside, after lining with brown paper, screwing them each way into the boards.

The door may have a latch or lock with a knob, but should in addition have two buttons on the inside, fixed so as to pull it shut tightly at top and bottom. A waste pipe should be attached to the sink and arranged to discharge through the floor. A cistern with pipe and tap can be fastened in the top of the dark room, if desired, or the room may be made with a flat roof, and a tank stand on it, though this is hardly advisable.

It is absolutely necessary that the room be well painted, four coats at first is not too many, and one coat twice a year will keep it in good condition.

A brick foundation should be laid so that no part of the room touches the ground.

Querl Made of Wood

"Querl" is the German name for a kitchen utensil which may be used as an egg-beater, potato-masher or a lemon-squeezer. For beating up an egg in a glass, mixing flour and water, or stirring cocoa or chocolate, it is better than anything on the market.

This utensil is made of hardwood, preferably maple or ash. A circular piece about 2 in. in diameter is cut from 1/2-in. stock and shaped like a star as shown in Fig. 1, and a 3/8-in. hole bored in the center for a handle. The handle should be at least 12 in. in length and fastened in the star as shown in Fig. 2.

In use, the star is placed in the dish containing the material to be beaten or mixed and the handle is rapidly rolled between the palms of the hands.

Contributed by W. Karl Hilbrich, Erie, Pennsylvania.

Occasionally one finds a piece of soldering to do which is impossible to reach with even the smallest of the ordinary soldering irons or coppers. If a length of copper wire as large as the job will permit and sufficiently long to admit being bent at one end to form a rough handle, and filed or dressed to a point on the other, is heated and tinned exactly as a regular copper should be, the work will cause no trouble on account of inaccessibility.

Contributed by E. G. Smith, Eureka Springs, Ark.

Collar Button Ends In Wood Stick

When an ink line is erased the roughened surface of the paper should be smoothed or polished so as to prevent the succeeding lines of ink from spreading. A convenient desk accessory for this purpose can be made of a short piece of hardwood and two bone collar buttons.

File off the head of one button at A and the base from another at B. Bore a small hole D and E in each end of the wood handle C and fasten the button parts in the holes with glue or sealing wax. The handle can be left the shape shown or tapered as desired. The small end is used for smoothing small erasures and the other end for larger surfaces.

Hairpin In Stick

An ordinary hairpin is driven part way into a small round piece of wood, about 3/8 in. in diameter and 2 or 2-1/2 in. long, for a handle, as shown in the sketch. The hairpin should be a very small size. To operate, simply insert the wire loop into the cherry where the stem has been pulled off and lift out the seed.

Contributed by L. L. Schweiger, Kansas City, Mo.

Shape of Tenon and Mortise

The illustration shows an unusual dovetail joint, which, when put together properly is a puzzle. The tenon or tongue of the joint is sloping on three surfaces and the mortise is cut sloping to match. The bottom surface of the mortise is the same width at both ends, the top being tapering toward the base of the tongue.

Contributed by Wm. D. Mitchell, Yonkers, New York.

Base Made of Corks

The many forms of round-bottomed glass bottles used in chemical laboratories require some special kind of support on which they can be safely placed from time to time when the chemist does not, for the moment, need them. These supports should not be made of any hard material nor should they be good conductors of heat, as such qualities would result in frequent breakage.

A French magazine suggests making the supports from the large corks of glass jars in which crystal chemicals are usually supplied from the dealers. The manner of making them is clearly shown in the sketch. Each cork is cut as in Fig. 1 and placed on a wire ring (Fig. 2) whose ends are twisted together and the last section of cork is cut through from the inner side to the center and thus fitted over the wire covering the twisted ends, which binds them together. The corks in use are shown in Fig. 3.

Artistic Flower Boxes

Instead of using an ordinary green-painted window box, why not make an artistic one in which the color does not clash with the plants contained in it but rather harmonizes with them.

Such a window box can be made by anyone having usual mechanical ability, and will furnish more opportunities for artistic and original design than many other articles of more complicated construction.

The box proper should be made a little shorter than the length of the window to allow for the extra space taken up in trimming and should be nearly equal in width to the sill, as shown in Fig. 1. If the sill is inclined, as is usually the case, the box will require a greater height in front, to make it set level, as shown in Fig. 2.

The box should be well nailed or screwed together and should then be painted all over to make it more durable. A number of 1/2-in. holes should be drilled in the bottom, to allow the excess water to run out and thus prevent rotting of the plants and box.

Having completed the bare box, it may be trimmed to suit the fancy of the maker. The design shown in Fig. 1 is very simple and easy to construct, but may be replaced with a panel or other design. One form of panel design is shown in Fig. 3.

Trimming having too rough a surface will be found unsuitable for this work as it is difficult to fasten and cannot be split as well as smooth trimming. It should be cut the proper length before being split and should be fastened with brads. The half-round hoops of barrels will be found very useful in trimming, especially for filling-in purposes, and by using them the operation of splitting is avoided. After the box is trimmed, the rustic work should be varnished, in order to thoroughly preserve it, as well as improve its appearance.

To the owner of a garden in a town where squirrels are protected by law, life in the summer time is a vexation. First the squirrels dig up the sweet corn and two or three replantings are necessary. When the corn is within two or three days of being suitable for cooking, the squirrels come in droves from far and near. They eat all they can and carry away the rest. When the corn is gone cucumbers, cabbages, etc., share the same fate, being partly eaten into. At the risk of being arrested for killing the squirrels I have used a small target rifle morning and night, but during my absence the devastation went on steadily. Last year they destroyed my entire corn crop. Traps do no good; can't use poison, too dangerous. But I have solved the difficulty; it's easy.

Shake cayenne pepper over the various vegetables which are being ruined, and observe results.

Pattern for Parts of the Electric Stove

The construction of an electric stove is very simple, and it can be made by any home mechanic having a vise and hand drill. The body is made of sheet or galvanized iron, cut out and drilled as shown in Fig. 1.

Each long projection represents a leg, which is bent at right angles on the center line by placing the metal in the jaws of a vise and hammering the metal over flat. If just the rim is gripped in the vise, it will give a rounding form to the lower part of the legs. The small projections are bent in to form a support for the bottom.

The bottom consists of a square piece of metal, as shown in Fig. 2. Holes are drilled near the edges for stove bolts to fasten it to the bottom projections. Two of the larger holes are used for the ends of the coiled rod and the other two for the heating-wire terminals. The latter holes should be well insulated with porcelain or mica. The top consists of a square piece of metal drilled as shown in Fig. 3. Four small ears are turned down to hold the top in place.

One end of the coiled rod is shown in Fig. 4. This illustrates how two pins are inserted in holes, drilled at right angles, to hold the coil on the bottom plate. The coiled rod is 3/16 in. in diameter and 27 in. long. The rod is wrapped with sheet asbestos, cut in 1/2-in. strips.

The length of the heating wire must be determined by a test. This wire can be purchased from electrical stores. Stovepipe wire will answer the purpose when regular heating wire cannot be obtained. The wire is coiled around the asbestos-covered rod, so that no coil will be in contact with another coil. If, by trial, the coil does not heat sufficiently, cut some of it off and try again. About 9-1/2 ft. of No. 26 gauge heating wire will be about right. The connection to an electric-lamp socket is made with ordinary flexible cord, to which is attached a screw plug for making connections.

Glass tumblers, tubing and fancy bottles are hard to clean by washing them in the ordinary way, as the parts are hard to reach with the fingers or a brush. The following solution makes an excellent cleaner that will remove dirt and grease from crevices and sharp corners. To 9 parts of water add 1 part of strong sulphuric acid. The acid should be added to the water slowly and not the water to the acid. Add as much bichromate of potash as the solution will dissolve. More bichromate of potash should be added as the precipitate is used in cleaning.

The chemicals can be purchased cheaply from a local drug store, and made up and kept in large bottles. The solution can be used over and over again.

Contributed by Loren Ward Des Moines, Iowa.

Diagram of Closing Door

When the neighborhood cats are retired for the night and there is nothing more to chase, my fox terrier seems to realize that his usefulness for the day is over and begs to be put in his kennel that he may not bark at the moon as some dogs are apt to do. This necessitates my putting him out at a time when it may not be convenient. Frequently in stormy weather this is a disagreeable duty and I found a way to obviate it by making a trapdoor device for his kennel as shown in the sketch whereby he may lock himself in when he crosses the threshold.

The outer half A of the hinged trapdoor is made heavier than the inner half B by a cleat, C, and a strip, D, to cause the door to swing shut. The tripper stick E is set between cleats C and F to hold the door open. When the dog steps on the inner half of the trapdoor B, it falls to stop G, releasing tripper stick E (which is heavier on the top end H) to cause it to fall clear of the path of the trapdoor. The door then swings shut in the direction of the arrow, the latch I engaging a slot in the door as it closes, and the dog has locked himself in for the night. The latch I is made of an old-fashioned gate latch which is mortised in the bottom joist of the kennel. When releasing the dog in the morning the door is set for the evening.

Contributed by Victor Labadie, Dallas, Texas.

Mix 2 lb. of whiting and 1/2 oz. of oleic acid with 1 gal. of gasoline. Stir and mix thoroughly. Soak pieces of gray outing flannel of the desired size—15 by 12 in. is a good size—in this compound. Wring the surplus fluid out and hang them up to dry, being careful to keep them away from the fire or an open flame. These cloths will speedily clean silver or plated ware and will not soil the hands.

In cleaning silver, it is best to wash it first in hot water and white soap and then use the polishing cloths. The cloths can be used until they are worn to shreds. Do not wash them. Knives, forks, spoons and other small pieces of silver will keep bright and free from tarnish if they are slipped into cases made from the gray outing flannel and treated with the compound. Separate bags for such pieces as the teapot, coffee pot, hot-water pot, cake basket and other large pieces of silverware will keep them bright and shining.

Contributed by Katharine D. Morse, Syracuse, N. Y.

Fig 2. Box Corner Makes a Book Holder

Books having a flexible back are difficult to hold in an upright position when copying from them. A makeshift combination of paperweights and other books is often used, but with unsatisfactory results.

The book-holder shown in the sketch will hold such books securely, allow the pages to be turned easily and conceal the smallest possible portion of each page.

The holder can be cut out of a box corner and fitted with two screw eyes, which have the part shown by the dotted lines at A (Fig. 1) removed. The length of the back board determines the slope for the book rest.

Contributed by James M. Kane, Doylestown, Pa.

It is aggravating to continually break the cork of the stock mucilage bottle because of its sticking to the neck of the bottle after a supply has been poured out. If a stove bolt is inserted lengthwise through the cork with a washer on each end and the nut screwed up tightly, as shown in the sketch, the cork may be made to last longer than the supply of mucilage and can be placed in a new bottle and used over and over again.

Invert a bottle on a piece of paper near the edge of a table top and ask anyone to remove the paper without overturning the bottle. They will at once jerk the paper with the result that the bottle will turn over. To remove the paper just strike the table top with your right fist while pulling the paper slowly with your left hand. As you strike the table the bottle will jump and release the paper.

Contributed by Maurice Baudier, New Orleans, La.

A bone collar button makes a good substitute for a plug in repairing a puncture in a single-tube bicycle tire.

The broom holder shown in the sketch is made of an ordinary hinge with one wing screwed to the wall. The loose wing has a large hole drilled in it to receive the handle of the broom. The manner of holding the broom is plainly shown in the sketch.

Contributed by Theodore L. Fisher; Waverly, Ill.

A correspondent of Camera Craft makes proofs from his developed, but unfixed, negatives, by squeezing a sheet of wet bromide paper into contact with the wet film and giving an exposure several times longer than would be required under ordinary conditions, using the paper dry. If the developer is well rinsed out of the film, the exposure to artificial light necessary to make a print will have no injurious effect upon the negative, which is, of course, later fixed and washed as usual.

A very useful stand for flower pots can be made of a piece of board supported by four clothes hooks. The top may be of any size suitable for the flower pot. The hooks which serve as legs are fastened to the under side of the board in the same manner as fastening the hook to a wall.

Contributed by Oliver S. Sprout, Harrisburg, Pa.

As an apparatus capable of exciting interest, probably nothing so easily constructed surpasses the harmonograph. Your attention will be completely absorbed in the ever changing, graceful sweep of the long pendulum, the gyrations of which are faithfully recorded in the resulting harmonogram.

A careless impetus given to the pendulum may result in a very beautiful harmonogram, but you may try innumerable times to duplicate this chance record without success. No two hamonograms are exactly alike. The harmonograph, while its pendulum swings in accordance with well known natural laws, is exceedingly erratic when it comes to obeying any preconceived calculations of its operator. In this uncertainty lies the charm. If time hangs heavily or a person is slightly nervous or uneasy, a harmonograph is a good prescription.

The prime essential in a well working harmonograph is a properly constructed universal joint. Where such a joint is made with pivots for its bearings, one pair of pivots are very liable to have more friction than the other, which retards the movement and causes the harmonograph to undergo a continuous change of axis. To obviate this difficulty, the joint should be made similar to those used on scales. The general appearance of such a joint is shown in the first illustration, Fig. 1. Stirrups A and B are made of 7/8 by 1/4-in. metal. Holes are drilled in each end of these stirrups and filed out as shown at C. The two holes shown in the center of the stirrup A are drilled to fasten the apparatus to the ceiling. Two corresponding holes are drilled in B to fasten the long pendulum F to the joint. The cross of the joint D has the ends shaped as shown at E. The rounded shoulder on E is to prevent the cross from becoming displaced by a jar or accident. The ends of the cross are inserted through the holes C of the stirrups, then slipped back so the knife edges engage in the V-shaped holes of the stirrups. The cross must be so made that the knife edges will be in the same plane. This can be determined by placing two of the knife edges on the jaws of a vise and then laying two rules across the other two edges. The rules should just touch the jaws of the vise and the two knife edges of the cross. This makes a universal joint almost free from friction and, what is most important, prevents the pendulum from twisting on its own axis.

The pendulum F should be made of ash or oak, 1-3/4 by 2 in., with a length depending on the height of the ceiling. A length of 7 ft. is about right for a 10-ft. ceiling.

A small table or platform, K, as shown in the lower part of Fig. 1, is fastened to the lower end of the pendulum as a support for the cards on which harmonograms are made. A weight, G, of about 30 or 40 lb.-a box filled with small weights will do—is attached to the pendulum just above the table. Another weight of about 10 lb. is attached as shown at H. A pedestal, J, provides a means of support for the stylus. The stylus arm should have pin-point bearings, to prevent any side motion.

The length of the short pendulum H, which can be regulated, as shown in Fig. 1, should bear a certain and exactly fixed relation to the length of the main pendulum, for the swinging times of pendulums are inversely proportionate to their lengths, and unless the shorter pendulum is, for instance, exactly one-third, one-fourth, one-fifth, etc., as long as the other, that is, makes respectively 3, 4 or 5 swings to one swing of the long pendulum, they will not harmonize and a perfect harmonogram is not obtained.

Lines Made with the Harmonograph

A good stylus to contain the ink is easily made from a glass tube 1/4 in. in diameter. Heat the tube in an alcohol or Bunsen flame and then, by drawing the two portions apart and twisting at the same time, the tube may be drawn to a sharp point. An opening of any desired size is made in the point by rubbing it on a whetstone. Owing to the fact that the style of universal joint described has so little friction, the stylus point must be very fine, or the lines will overlap and blur. A small weight, such as a shoe buttoner, placed on the arm near the stylus will cause enough friction to make the pendulum "die" faster and thus remedy the trouble.

Contributed by Wm. R. Ingham, Rosemont, Arizona.

In arts and crafts work, occasion often arises to cut a perfectly circular hole in sheet copper or brass. To saw and file it out takes time and skill. Holes up to 3 in. in diameter can be cut quickly and accurately with an ordinary expansive bit.

Fasten the sheet metal to a block of wood with handscrews or a vise. Punch a hole, with a nail set or punch, in the center of the circle to be cut, large enough to receive the spur of the expansive bit. A few turns of the brace will cut out the circle and leave a smooth edge.

Contributed by James T. Gaffney, Chicago.

The Key Card

A key card for use in correspondence on postals that makes the matter unreadable unless the recipient has a duplicate key card is made as follows: Rule two cards the size of postal, one for the sender and one for the receiver, dividing them into quarters. These quarters are subsequently divided into any convenient number of rectangular parts-six in this case.

These parts are numbered from one to six in each quarter beginning at the outside corners and following in the same order in each quarter. Cut out one rectangle of each number with a sharp knife, distributing them over the whole card. Then put a prominent figure 1 at the top of one side, 2 at the bottom and 3 and 4 on the other side. The numbering and the cutouts are shown in Fig. 1. The two key cards are made alike.

The key card is used by placing it over a postal with the figure 1 at the top and writing in the spaces from left to right as usual, Fig. 3, then put 2 at the top, Fig. 4, and proceed as before, then 3 as in Fig. 5, and 4 as in Fig. 6. The result will be a jumble of words as shown in Fig. 2, which cannot be read to make any sense except by use of a key card.

Contributed by W.J. Morey, Chicago.

The sketch shows an easily made, quick-working wood vise that has proved very satisfactory. The usual screw is replaced by an open bar held on one end by a wedge-shaped block, and the excess taken up on the other end by an eccentric lever. The wedge is worked by a string passing through the top of the bench and should be weighted on the other end to facilitate the automatic downward movement. The capacity of the vise, of course, depends on the size and shape of the wedge-shaped block.

Contributed by J.H. Cruger, Cape May City, N.J.

After some experimenting to secure a blue tone on bromide prints, a correspondent of the Photographic Times produced a very pleasing bluish green tint by immersing the prints in a solution composed of 30 gr. of ferricyanide of potash, 30 gr. citrate of iron and ammonia, 1/2 oz. acetic acid and 4 oz. of water. After securing the tint desired, remove the prints, rinse them in clean water for a few minutes, and then place them in a dilute solution of hydrochloric acid. Wash the prints thoroughly and hang them up with clips to dry.

When cutting a loaf of bread do not slice it from the outer crusted end. Cut through the center, then cut slices from the center toward the ends. The two cut surfaces can be placed together, thus excluding the air and keeping the bread fresh as long as there is any left to slice.

Contributed by L. Alberta Norrell, Augusta, Ga.

Detail of Toaster

Toaster Complete

The electric toaster shown in the sketch is not hard to make. The framework comprising the base and the two uprights may be made either of hardwood or asbestos board, says Popular Electricity. If constructed of the former, the portion of the base under the coil, and the inside surfaces of the two uprights should be covered with a 1/8-in. sheet of well made asbestos paper, or thin asbestos board may be substituted for this lining. Asbestos board is to be preferred, and this material in almost any degree of hardness may be purchased. It can be worked into shape and will hold wood screws. The detail drawing gives all dimensions necessary to shape the wood or asbestos board.

After preparing the base and uprights, drill 15 holes, 1/4 in. deep, into the inside face of each upright to support the No. 6 gauge wires shown. The wires at the top and bottom for holding the resistance wire are covered with asbestos paper and the holes for these wires are 3/4 in. from the top and bottom, respectively, of the uprights. The wires that form the cage about the heater coil and are used for a support for the toast are 15 pieces of No. 6 gauge iron wire each 8 in. long. The screws that hold the uprights in position should have the heads countersunk on the under side of the base. The binding-posts should now be set in position and their protecting covering containing the reinforced cord left until the other parts are finished.

To assemble, secure one upright in position using 1-1/2 in. wood-screws. Place the other upright where it belongs without fastening it and put the stretcher wires for holding the resistance wire in place. Put the asbestos paper on these and with the assistance of a helper begin winding on the heater coil. Use 80 ft. of 18-per-cent No. 22 gauge German-silver wire. Wind the successive turns of wire so they will not touch each other and fasten at each end with a turn or two of No. 16 gauge copper wire. When this is complete have the helper hold the stretcher wires while you tip the unfastened upright out and insert the wires of the cage, then fasten the upright in place.

The wire from the binding-posts to the coil may be what is known underwriters' wire or asbestos-covered wire No. 14 gauge, which is held in place by double-headed tacks containing an insulation at the head. These may be procured from electrical supply houses. Connect the reinforced cord and terminals to the binding screws and fasten the cover in place. This toaster will take four amperes on [a] 110-volt circuit.

Empty Cigar Boxes Used for Drawers

One of the most convenient adjuncts to an amateur's workbench is a cabinet of some sort in which to keep nails, rivets, screws, etc., instead of leaving them scattered all about the bench. A very easily made cabinet for this purpose is shown in the accompanying illustration. The case may be made of 1/2-in. white pine or white wood of a suitable size to hold the required number of drawers which slide on strips of the same material, cut and dressed 1/2 in. square. The drawers are made of empty cigar boxes of uniform size, which, if one is not a smoker, may be readily obtained from any cigar dealer, as they are usually thrown away when empty.

Small knobs may be added if desired, but these are not necessary, as the spaces shown between the drawers give ample room to grasp them with the fingers. Labels of some kind are needed, and one of the neatest things for this purpose is the embossed aluminum label, such as is stamped by the well known penny-in-the-slot machines to be found in many railroad stations and amusement places.

Contributed by Frederick E. Ward, Ampere, N. Y.

Photograph prints can be kept from curling when dry, by giving them the same treatment as was once used on films. Immerse for 5 minutes in a bath made by adding 1/4 oz. of glycerine to 16 oz. of water.

Successful soldering will present no serious difficulties to anyone who will follow a few simple directions. Certain metals are easier to join with solder than others and some cannot be soldered at all. Copper, brass, zinc, tin, lead, galvanized iron, gold and silver or any combination of these metals can be easily soldered, while iron and aluminum are common metals that cannot be soldered.

It is necessary to possess a soldering copper, a piece of solder, tinner's acid, sandpaper or steel wool, a small file and a piece of sal ammoniac. If the soldering copper is an old one, or has become corroded, it must be ground or filed to a point. Heat it until hot (not red hot), melt a little solder on the sal ammoniac, and rub the point of the copper on it, turning the copper over to thoroughly tin the point on each face. This process is known as tinning the iron and is very necessary to successful work.

After the copper is tinned you may place it in the fire again, being careful about the heat, as too hot an iron will burn off the tinning.

The parts to be soldered must be thoroughly cleaned by sandpapering or the use of steel wool until the metal shows up bright. Then apply the acid only to the parts to be soldered with a small stiff brush or a small piece of cloth fastened to a stick, or in a bent piece of tin to form a swab.

Tinner's acid is made by putting as much zinc in commercial muriatic acid as will dissolve. This process is best accomplished in an open earthenware dish. After the acid has ceased to boil and becomes cool it may be poured into a wide-mouthed bottle which has a good top or stopper, and labeled "Poison."

Place the parts to be soldered in their correct position and apply the hot copper to the solder, then to the joint to be soldered, following around with the copper and applying solder as is necessary.

In joining large pieces it is best to "stick" them together in several places to hold the work before trying to get all around them. A little practice will soon teach the requisite amount of solder and the smoothness required for a good job.

In soldering galvanized iron, the pure muriatic acid should be used, particularly so when the iron has once been used.

C. G. S., Eureka Springs, Ark.

Clip on the Washboard

When using a washboard it will continually slip down in the tub. This is considerable annoyance, especially if a large tub is used. The washboard can be kept in place with small metal hooks, as shown in the sketch. Two of these are fastened to the back of the washboard in the right place to keep it at the proper slant.

Contributed by W. A. Jaquythe, Richmond, California.

Details of the Wall Bracket

The shelf consists of six pieces of wood A, B, C, D, E and F. The material can be of any wood. I have one made of mahogany finished in natural color, and one made of poplar finished black. The dimensions given in the detail drawings are sufficient for anyone to make this bracket. The amount of material required is very small and can be made from scrap, or purchased from a mill surfaced and sanded. The parts are put together with dowel pins.

Contributed by A. Larson, Kenosha, Wis.

Tools for Forming the Ring

While the wearing of copper rings for rheumatism may be a foolish notion, yet there is a certain galvanic action set up by the contact of the acid in the system of the afflicted person with the metal of the ring. Apart from this, however, a ring may be made from any metal, such as copper, brass and silver, if such metals are in plate or sheet form, by the following method:

All the tools necessary are a die and punch which are simple to make and will form a ring that will fit the average finger. Take a 3/4-in. nut, B, Fig. 1, and drill out the threads. This will leave a clear hole, 7/8 in. in diameter, or a hole drilled the desired size in a piece of iron plate will do as well. Countersink the top of the hole so that the full diameter of the countersink will be 1-1/4 in. This completes the die. The punch A, is made of a piece of 5/8 in. round iron, slightly rounded on the end so that it will not cut through the metal disk. The dimensions shown in Fig. 1 can be changed to suit the size of the finger to be fitted. {40} The metal used should be about 1/16 in. thick and 1-1/4 in. in diameter. Anneal it properly by heating and plunging in water. Lay it on the die so that it will fit nicely in the countersink and drive it through the hole by striking the punch with a hammer. Hold the punch as nearly central as possible when starting to drive the metal through the hole. The disk will come out pan shaped, C, and it is only necessary to remove the bottom of the pan to have a band which will leave a hole 5/8 in. in diameter and 1-1/4 in. wide. Place the band, D, Fig. 2, on a stick so that the edges can be filed and rounded to shape. Finish with fine emery cloth and polish. Brass rings can be plated when finished.

Contributed by H. W. Hankin, Troy, N. Y.

A great many readers of Popular Mechanics Magazine save their copies and have them bound in book form and some keep them without binding. The bound volumes make an attractive library and will always be valuable works of reference along mechanical lines. I bind my magazines at home evenings, with good results. Six issues make a well proportioned book, which gives two bound volumes each year.

The covers of the magazines are removed, the wire binders pulled out with a pair of pliers and the advertising pages removed from both sides, after which it will be found that the remainder is in sections, each section containing four double leaves or sixteen pages. These sections are each removed in turn from the others, using a pocket knife to separate them if they stick, and each section is placed as they were in the magazine upon each preceding one until all six numbers have been prepared. If started with the January or the July issue, the pages will be numbered consecutively through the entire pages of the six issues.

Frame For Sewing Sections

The sections are then prepared for sewing. They are evened up on the edges by jarring on a flat surface. They are then placed between two pieces of board and all clamped in a vise. Five cuts, 1/8 in. deep, are made with a saw across the back of the sections, as shown in Fig. 1. Heavy plain paper is used for the flyleaves. The paper is cut double the same as the leaves comprising the sections, making either one or two double sections for each side as desired.

A frame for sewing will have to be made as shown in Fig. 2 before the work can be continued on the book. The frame is easily made of four pieces of wood. The bottom piece A should be a little larger than the book. The two upright pieces B are nailed to the outside edge, and a third piece, C, is nailed across the top. Small nails are driven part way into the base C to correspond to the saw cuts in the sections. A piece of soft fiber string is stretched from each nail to the crosspiece C and tied.

Coarse white thread, size 16 or larger, is used for the sewing material. Start with the front of the book. Be sure that all sections are in their right places and that the flyleaves are provided in the front and back. Take the sections of the flyleaves on top, which should be notched the same as the saw cuts in the book sections, and place them against the strings in the frame. Place the left hand on the inside of the leaves where they are folded and start a blunt needle, threaded double, through the notch on the left side of the string No. 1 in Fig. 2. Take hold of the needle with the right hand and pass it to the left around the string No. 1, then back through the notch on the right side. Fasten the thread by tying or making a knot in the end and passing the needle through it. After drawing the thread tightly, pass the needle through the notch on the left side of the string No. 2, passing it around the string and tying in the same manner as for No. 1. {41} Each section is fastened to the five strings in the same manner, the thread being carried across from each tie from No. 1 to 2 then to 3 and so on until all strings are tied. The string No. 5 is treated in the same manner only that the needle is run through on the left side of the string a second time, leaving the needle on the outside in position for the next section, which is fastened the same as the first, the needle being passed through the notch on the right side of the string No. 5, and then to string No.4, passing around on the right side and back on the left and so on. Keep the thread drawn up tightly all the time.

After the sewing is completed cut the strings, allowing about 2 in. of the ends extending on each side. The fibers of these ends are separated and combed out so that they can be glued to the covers to serve as a hinge. A piece of cheesecloth is cut to the size of the back and glued to it. Ordinary liquid glue is the best adhesive to use.

Procure heavy cardboard for the covers and cut two pieces 1/2 in. longer and just the same width as the magazine pages. The covering can be of cloth, leather or paper according to the taste and resources of the maker. The covering should be cut out 1 in. larger on all edges than both covers and space on the back. Place the cardboard covers on the book, allowing a margin of 1/4 in. on all edges except the back, and measure the distance between the back edges of the covers across the back of the book.

Place the cardboard covers on the back of the covering the proper distance apart as measured for the back, and mark around each one. Spread a thin coat of glue on the surface of each and lay them on by the marks made. Cut a notch out of the covering so it will fold in, and, after gluing a strip of paper to the covering between the covers to strengthen the back, fold over the outside edges of the covering and glue it down all around.

The Bound Book

Place the cover on the book in the right position, glue the hinges fast to the inside of the covers, then glue the first flyleaf to the inside of the cover on both front and back and place the whole under a weight until dry.

Contributed by Clyde E. Divine, College View, Nebr.

Metal Parts Screwed on Leather Hinge

A method of making a leather hinge work as well as an ordinary steel butt is to cover the wings with sheet metal. The metal can be fastened with nails or screws over the parts of the leather attached to the wood. Tinplate, iron hoops, zinc or thin brass cut in neat designs will make a leather hinge appear as well as a metal hinge.

Contributed by Tom Hutchinson, Encanto, Cal.

A hot-water bottle held against a porous plaster will assist in quickly removing it from the skin.

Hacksaw Frame and Blade

For the frame use 3/8-in. round iron, bending it as shown in the diagram and filing a knob on each end, at opposite sides to each other, on which to hook the blade.

For the blade an old talking-machine spring or a clock spring will do nicely. Heat the spring enough to take some of the temper out of it, in order to drill the holes in the ends, as shown, and file in the teeth. Make the blade 12 in. long, with 10 teeth to the inch. A and B show how the blade fits on the frame.

Contributed by Willard J. Hays, Summitville, Ohio.

Toy Cannon

A cannon like the one in the cut may be made from a piece of 1-in. hydraulic pipe, A, with a steel sleeve, B, and a long thread plug, C. Be sure to get hydraulic pipe, or double extra heavy, as it is sometimes called, as common gas pipe is entirely too light for this purpose. Don't have the pipe too long or the cannon will not make as much noise. Seven or eight inches is about the right length for a 1-in. bore. Screw the plug and pipe up tightly and then drill a 1/16-in. fuse hole at D.

If desired the cannon may be mounted on a block of wood, F, by means of a U-bolt or large staple, E.

Contributed by Carson Birkhead, Moorhead, Miss.

Reverse for Motor

An easy way of making a controlling and reversing device for small motors is as follows:

Cut a piece of wood (A) about 6 in. by 4-1/2 in., and 1/4 in. thick, and another piece (B) 6 in. by 1 in., and 1/4 in. thick. Drive a nail through this near the center for a pivot (C). To the under side of one end nail a copper brush (D) to extend out about an inch. On the upper side, at the same end, nail another brush (E) so that it projects at both sides and is bent down to the level of the end brush. Then on the board put a semi-circle of brass-headed tacks as shown at F, leaving a small space at the middle and placing five tacks on either side, so that the end brush will come in contact with each one. Connect these tacks on the under side of the board with coils of German-silver wire, using about 8 in. of wire to each coil. Fix these by soldering or bending over the ends of the tacks. Then nail two strips of copper (G) in such position that the side brush will remain on the one as long as the end brush remains on the tacks on that side.

Put sides about 1-1/2 in. high around this apparatus, raising the board a little from the bottom to allow room for the coil. A lid may be added if desired. Connect up as shown.

Contributed by Chas. H. Boyd, Philadelphia.

Wiring Plan for Water Rheostat

The materials necessary are: One 5-point wood-base switch, 4 jars, some sheet copper or brass for plates, about 5 ft. of rubber-covered wire, and some No. 18 gauge wire for the wiring.

The size of the jars depends on the voltage. If you are going to use a current of low tension, as from batteries, the jars need not be very large, but if you intend to use the electric light current of 110 voltage it will be necessary to use large jars or wooden boxes made watertight, which will hold about 6 or 7 gal. Each jar to be filled with 20 parts water to 1 part sulphuric acid. Jars are set in a row in some convenient place out of the way.

Next cut out eight copper or brass disks, two for each jar. Their size also depends on the voltage. The disks that are placed in the lower part of the jars are connected with a rubber covered wire extending a little above the top of the jar.

To wire the apparatus, refer to the sketch and you will see that jar No. 1 is connected to point No. 1 on switch; No. 2, on No. 2, and so on until all is complete and we have one remaining point on switch. Above the jars place a wire to suspend the other or top disks in the solution. This wire is also connected to one terminal on the motor and to remaining point on switch. The arm of the switch is connected to one terminal of battery, or source of current, and the other terminal connected direct to remaining terminal of motor.

Put arm of switch on point No. 1 and lower one of the top disks in jar No. 1 and make contact with wire above jars. The current then will flow through the motor. The speed for each point can be determined by lowering top disks in jars. The top disk in jar No. 2 is lower down than in No. 1 and so on for No. 3 and No. 4. The connection between point No. 5 on switch, direct to wire across jars, gives full current and full speed.

Construction a "Winner" Toboggan Sled

The first object of the builder of a sled should be to have a "winner" both in speed and appearance. The accompanying instructions for building a sled are designed to produce these results.

The sled completed should be 15 ft. 2 in. long by 22 in. wide, with the cushion about 15 in. above the ground. For the baseboard select a pine board 15 ft. long, 11 in. wide and 2 in. thick, and plane it on all edges. Fit up the baseboard with ten oak foot-rests 22 in. long, 3 in. wide and 3/4 in. thick. Fasten them on the under side of the baseboard at right angles to its length and 16 in. apart, beginning at the rear. At the front 24 or 26 in. will be left without cross bars for fitting on the auto front. On the upper side of the cross bars at their ends on each side screw a piece of oak 1 in. square by 14 ft. long. On the upper side of the baseboard at its edge on each side screw an oak strip 3 in. wide by 3/4 in. thick and the length of the sled from the back to the auto front. These are to keep the cushion from falling out. See Fig. 1. For the back of the sled use the upper part of a child's high chair, taking out the spindles and resetting them in the rear end of the baseboard. Cover up the outside of the spindles with a piece of galvanized iron.

The construction of the runners is shown by Figs. 2 and 3. The stock required for them is oak, two pieces 30 in. by 5 in. by 1-1/4 in., two pieces 34 in. by 5 in. by 1-1/4 in., two pieces 14 in. by 6 in. by 2 in., and four pieces 14 in. by 2 in. by 1 in. They should be put together with large screws about 3 in. long. Use no nails, as they are not substantial enough. In proportioning them the points A, B and C, Fig. 2, are important. For the front runners these measurements are: A, 30 in.; B, 4 in.; C, 15-1/2 in., and for the rear runners: A, 34 in.; B, 7 in.; C, 16-1/2 in. The screw eyes indicated must be placed in a straight line and the holes for them carefully centered. A variation of 1/16 in. one way or another would cause a great deal of trouble. For the steel runners use 3/8 in. cold-rolled steel flattened at the ends for screw holes. Use no screws on the running surface, however, as they "snatch" the ice.

The mechanism of the front steering gear is shown at Fig. 3. A 3/4-in. steel rod makes a good steering rod. Flatten the steering rod at one end and sink it into the wood. Hold it in place by means of an iron plate drilled to receive the rod and screwed to block X. An iron washer, Z, is used to reduce friction; bevel block K to give a rocker motion. Equip block X with screw eyes, making them clear those in the front runner, and bolt through. For the rear runner put a block with screw eyes on the baseboard and run a bolt through.

Construct the auto front (Fig. 4) of 3/4-in. oak boards. The illustration shows how to shape it. Bevel it toward all sides and keep the edges sharp, as sharp edges are best suited for the brass trimmings which are to be added. When the auto front is in place enamel the sled either a dark maroon or a creamy white. First sandpaper all the wood, then apply a coat of thin enamel. Let stand for three days and apply another coat. Three coats of enamel and one of thin varnish will make a fine-looking sled. For the brass trimmings use No. 27 B. & S. sheet brass 1 in. wide on all the front edges and pieces 3 in. square on the cross bars to rest the feet against. On the door of the auto front put the monogram of the owner or owners of the sled, cutting it out of sheet brass.

For the steering-wheel procure an old freight-car "brake" wheel, brass plated. Fasten a horn, such as used on automobiles, to the wheel.

Make the cushion of leather and stuff it with hair. The best way is to get some strong, cheap material, such as burlap, sew up one end and make in the form of an oblong bag. Stuff this as tightly as possible with hair. Then get some upholstery buttons, fasten a cord through the loop, bring the cord through to the underside of the cushion, and fasten the button by slipping a nail through the knot. Then put a leather covering over the burlap, sewing it to the burlap on the under side. Make the cushion for the back in the same way. On top of the cushion supports run a brass tube to serve the double purpose of holding the cushion down and affording something to hold on to.

If desired, bicycle lamps may be fastened to the front end, to improve the appearance, and it is well to have a light of some kind at the back to avoid the danger of rear-end collisions.

The door of the auto front should be hinged and provided with a lock so that skates, parcels, overshoes, lunch, etc. may be stowed within. A silk pennant with a monogram adds to the appearance.

If desired, a brake may be added to the sled. This can be a wrought-iron lever 1-1/2 in. by 1/2 in. by 30 in. long, so pivoted that moving the handle will cause the end to scrape the ice. This sled can be made without lamps and horn at a cost of about $15, or with these for $25, and the pleasure derived from it well repays the builder. If the expense is greater than one can afford, a number of boys may share in the ownership.

Scrape off the bark just enough to come to the first light under coating, which is somewhat moist. With a lead pencil make an outline of the inscription to be burnt on the tree and bring, the rays of a large magnifying glass not quite to a fine focus on the same. The tree will be burnt along the pencil marks, and if the glass is not held in one spot too long, the inscription will be burnt in as evenly as if it had been written.

Contributed by Stewart H. Leland, Lexington, Ill.

Making Model Wheels

To make small models sundry small gears and racks are required, either cut for the place or by using the parts from an old clock. With no other tools than a hacksaw, some files, a compass, and with the exercise of a little patience and moderate skill, very good teeth may be cut on blank wheels.

First take the case of a small gearwheel, say 1 in. outside diameter and 1/16 in. thick, with twenty-four teeth. Draw a circle on paper, the same diameter as the wheel. Divide the circumference into the number of parts desired, by drawing diameters, Fig. 1. The distance AB will be approximately the pitch. Now describe a smaller circle for the base of the teeth and halfway between these circles may be taken as the pitch circle.

Now describe a circle the same size as the largest circle on a piece of 1/16-in. sheet metal, and having cut it out and filed it up to this circle, fasten the marked-out paper circle accurately over it with glue. Saw-cuts can now be made down the diameters to the smaller circle with the aid of a saw guide, Fig. 2, made from 1/16-in. mild steel or iron. This guide should have a beveled edge, E, from F to G, to lay along the line on which the saw-cut is to be made. The straight-edge, CD, should be set back one-half the thickness of the saw-blades, so that the center of the blade, when flat against it, will be over the line FG. A small clearance space, FC, must be made to allow the teeth of the saw to pass.

The guide should then be placed along one of the diameters and held in position until gripped in the vise, Fig. 3. The first tooth may now be cut, care being taken to keep the blade of the saw flat up to the guiding edge. The Model Engineer, London, says if this is done and the saw-guide well made, the cut will be central on the line, and if the marking-out is correct the teeth will be quite uniform all the way round. A small ward file will be needed to finish off the teeth to their proper shape and thickness.

In making a worm wheel the cuts must be taken in a sloping direction, the slope and pitch depending on the slope and pitch of the worm thread, which, though more difficult, may also be cut with a hacksaw and file.

A bevel wheel should be cut in the same manner as the spur wheel, but the cut should be deeper on the side which has the larger diameter. To cut a rack the pitch should be marked along the side, and the guide and saw used as before (Fig. 4).

Four Photos on One Plate

Secure two extra slides for the plate holders and cut one corner out on one of them, as shown in Fig. 1. Make a hole in the other, as shown in Fig. 2. With a lead pencil draw on the ground glass one line vertical and one horizontal, each in the center. This will divide the ground glass into four equal parts.

Focus the camera in the usual manner, but get the picture desired to fill only one of the parts on the ground glass. Place the plate-holder in position and draw the regular slide; substitute one of the slides prepared and expose in the usual way.

If a small picture is to be made in the lower left-hand corner of the plate, place the prepared slide with the corner cut, as shown in Fig. 1. The slide may be turned over for the upper left hand corner and then changed for slide shown in Fig. 2 for the upper and lower right-hand corners.

Take a jump-spark coil and connect it up with a battery and start the vibrator. Then take one outlet wire, R, and connect to one side of a 2-cp. electric lamp, and the other outlet wire, B, hold in one hand, and press all fingers of the other hand on globe at point A. A bright, blue light will come from the wires in the lamp to the surface of the globe where the fingers touch. No shock will be perceptible.

A Unique Battery

The materials necessary for performing this experiment are: Telephone receiver, transmitter, some wire and some carbons, either the pencils for arc lamps, or ones taken from old dry batteries will do.

Run a line from the inside of the house to the inside of some other building and fasten it to one terminal of the receiver. To the other terminal fasten another piece of wire and ground it on the water faucet in the house. If there is no faucet in the house, ground it with a large piece of zinc.

Fasten the other end to one terminal of the transmitter and from the other terminal of the same run a wire into the ground. The ground here should consist either of a large piece of carbon, or several pieces bound tightly together.

If a person speak into the transmitter, one at the receiver can hear what is said, even though there are no batteries in the circuit. It is a well known fact that two telephone receivers connected up in this way will transmit words between two persons, for the voice vibrating the diaphragm causes an inductive current to flow and the other receiver copies these vibrations. But in this experiment, a transmitter which induces no current is used. Do the carbon and the zinc and the moist earth form a battery?

Contributed by Wm. J. Slattery, Emsworth, Pa.

Electric Fire Alarm

An electrical device for the barn that will give an alarm in case of fire is shown in the accompanying diagram. A is a wooden block, which is fastened under the loft at a gable end of the barn; B is an iron weight attached to the string C, and this string passes up through the barn to the roof, then over a hook or pulley and across the barn, under the gable, and is fastened to the opposite end of the barn.

D D are binding posts for electric wires. They have screw ends, as shown, by which means they are fastened to the wooden block A. They also hold the brass piece E and the strip of spring brass F in place against the wooden block. G is a leather strap fastened to the weight B and the spring F connected to the latter by a small sink bolt.

At the house an electric bell is placed wherever convenient. Several battery cells, of course, are also needed. Dry batteries are most convenient. The battery cells and bell are connected in the usual manner, and one wire from the bell and one from the battery are strung to the barn and connected to the binding posts D D.

If a fire occurs in the hay-mow the blaze will generally shoot toward the gable soon after it starts, and will then burn the string C, which allows the weight B to fall and pull the brass spring against the iron piece E, which closes the circuit and rings the bell in the house.

If desired, the string may be stretched back and forth under the roof several times or drawn through any place that is in danger of fire.

Contributed by Geo. B. Wrenn, Ashland, Ohio.

Electric Furnace

Take a block of wood and shape into a core. One like a loaf of bread, and about that size, serves admirably. Wrap a layer of asbestos around it and cover this with a thin layer of plaster-of-paris. When the plaster is nearly dry wind a coil of No. 36 wire around it, taking care that the wire does not touch itself anywhere. Put another course of plaster-of-paris on this, and again wind the wire around it. Continue the process of alternate layers of plaster and wire until 500 ft. or more of the latter has been used, leaving about 10 in. at each end for terminals. Then set the whole core away to dry.

For a base use a pine board 10 in. by 12 in. by 1 in. Bore four holes at one end for binding-posts, as indicated by E E. Connect the holes in pairs by ordinary house fuse wire. At one side secure two receptacles, B B, and one single post switch, C. Place another switch at I and another binding-post at F. The oven is now ready to be connected.

Withdraw the wooden core from the coils of wire and secure the latter by bands of tin to the board. Connect the ends of the wire to binding-posts E and F, as shown. From the other set of binding-posts, E, run a No. 12 or No. 14 wire, connecting lamp receptacles, B B, and switch, C, in parallel. Connect these three to switch, D, in series with binding-post, F, the terminal of the coil. Place 16-cp. lights in the receptacles and connect the fuses with a 110-volt lighting circuit. The apparatus is now ready for operation. Turn on switch, D, and the lamps, while C is open. The coil will commence to become warm, soon drying out the plaster-of-paris. To obtain more heat open one lamp, and to obtain still more open the other and close switch C.

Contributed by Eugene Tuttles, Jr., Newark, Ohio.

Complete Ammeter and Details

Every amateur mechanic who performs electrical experiments will find use for an ammeter, and for the benefit of those who wish to construct such an instrument the following description is given: The operative principle of this instrument is the same as that of a galvanometer, except that its working position is not confined to the magnetic meridian. This is accomplished by making the needle revolve in a vertical instead of a horizontal plane. The only adjustment necessary is that of leveling, which is accomplished by turning the thumbscrew shown at A, Fig. 1, until the hand points to zero on the scale.

First make a support, Fig. 2, by bending a piece of sheet brass to the shape indicated and tapping for the screws CC. These should have hollow ends, as shown, for the purpose of receiving the pivoted axle which supports the hand. The core, Fig. 3, is made of iron. It is 1 in. long, 1/4 in. wide and 1/8 in. thick. At a point a little above the center, drill a hole as shown at H, and through this hole drive a piece of knitting-needle about 1/2 in. long, or long enough to reach between the two screws shown in Fig. 2. The ends of this small axle should be ground pointed and should turn easily in the cavities, as the sensitiveness of the instrument depends on the ease with which this axle turns.

After assembling the core as shown in Fig. 4, it should be filed a little at one end until it assumes the position indicated. The pointer or hand, Fig. 5, is made of wire, aluminum being preferable for this purpose, although copper or steel will do. Make the wire 4-1/2 in. long and make a loop, D, 1/2 in. from the lower end. Solder to the short end a piece of brass, E, of such weight that it will exactly balance the weight of the hand. This is slipped on the pivot, and the whole thing is again placed in position in the support. If the pointer is correctly balanced it should take the position shown in Fig. 1, but if it is not exactly right a little filing will bring it near enough so that it may be corrected by the adjusting-screw.

Next make a brass frame as shown in Fig. 6. This may be made of wood, although brass is better, as the eddy currents set up in a conductor surrounding a magnet tend to stop oscillation of the magnet. (The core is magnetized when a current flows through the instrument.) The brass frame is wound with magnet wire, the size depending on the number of amperes to be measured. Mine is wound with two layers of No. 14 wire, 10 turns to each layer, and is about right for ordinary experimental purposes. The ends of the wire are fastened to the binding posts B and C, Fig. 1.

A wooden box, D, is then made and provided with a glass front. A piece of paper is pasted on a piece of wood, which is then fastened in the box in such a position that the hand or pointer will lie close to the paper scale. The box is 5-1/2 in. high, 4 in. wide and 1-3/4 in. deep, inside measurements. After everything is assembled put a drop of solder on the loop at D, Fig. 5, to prevent it turning on the axle.

To calibrate the instrument connect as shown in Fig. 7, where A is the homemade ammeter; B, a standard ammeter; C, a variable resistance, and D, a battery, consisting of three or more cells connected in multiple. Throw in enough resistance to make the standard instrument read 1 ohm [sic: ampere] and then put a mark on the paper scale of the instrument to be calibrated. Continue in this way with 2 amperes, 3 amperes, 4 amperes, etc., until the scale is full. To make a voltmeter out of this instrument, wind with plenty of No. 36 magnet wire instead of No. 14, or if it is desired to make an instrument for measuring both volts and amperes, use both windings and connect to two pairs of binding posts.

Contributed by J.E. Dussault, Montreal.

In making models of machines it is often necessary to contrive some method for a 3 or 4-way valve or cock. To make one, secure a pet cock and drill and tap hole through, as shown in the cut. If for 3-way, drill in only to the opening already through, but if for a 4-way, drill through the entire case and valve. Be sure to have valve B turned so as to drill at right angles to the opening through it. After drilling, remove the valve, take off the burr with a piece of emery paper and replace ready for work.

Arc-Light Motor and Water Rheostat

An electric-light circuit will be found much less expensive than batteries for performing electrical experiments. The sketch shows how a small arc light and motor may be connected to the light socket, A. The light is removed and a plug with wire connections is put in its place. One wire runs to the switch, B, and the other connects with the water rheostat, which is used for reducing the current.

A tin can, C is filled nearly to the top with salt water, and a metal rod, D, is passed through a piece of wood fastened at the top of the can. When the metal rod is lowered the current increases, and as it is withdrawn the current grows weaker. In this way the desired amount of current can be obtained. By connecting the motor, E, and the arc light, F, as shown, either one may be operated by turning switch B to the corresponding point. The arc light is easily made by fastening two electric light carbons in a wooden frame like that shown. To start the light, turn the current on strong and bring the points of the carbons together; then separate slightly by twisting the upper carbon and at the same time drawing it through the hole.

Details of Interrupter

The Completed Instrument

The Wenult interrupter is an instrument much used on large coils and is far more efficient than the usual form of vibrators. It can also be used with success on small coils as well as large. Although it is a costly instrument to purchase, it can be made with practically no expense and the construction is very simple.

First procure a wide-mouthed bottle about 4 in. high, provided with a rubber stopper. This stopper should be pierced, making two holes about 1/4 in. in diameter.

From a sheet of lead 1/16 in. in thickness cut a piece shaped like A, Fig. 1. Common tea lead folded several times will serve the purpose. When in the bottle this lead should be of such a size that it will only reach half way around, as shown in B. To insert the lead plate, roll it up so it will pass through the neck of the bottle, then smooth it out with a small stick until it fits against the side, leaving the small strip at the top projecting through the neck of the bottle. Bend this strip to one side and fit in the stopper, as shown in C. A small binding-post is fastened at the end of the strip.

Having fixed the lead plate in position, next get a piece of glass tube having a bore of about 1/32 of an inch in diameter. A piece of an old thermometer tube will serve this purpose. Insert this tube in the hole in the stopper farthest from the lead plate. Get a piece of wire that will fit the tube and about 6 in. long, and fasten a small binding-post on one end and stick the other into the tube. This wire should fit the hole in the tube so it can be easily moved. In the hole nearest the lead plate insert a small glass funnel.

The interrupter as it is when complete is shown at D, Fig. 1. Having finished the interrupter, connect it with the electric-light circuit as shown in Fig. 2. Fill the bottle with water to about the line as shown in D, Fig. 1. Adjust the wire in the small glass tube so that it projects about 1/8 in. Add sulphuric acid until the water level rises about 1/16 in. Turn on the current and press the button, B. If all adjustments are correct, there will be a loud crackling noise from the interrupter, a violet flame will appear at the end of the wire and a hot spark will pass between the secondary terminals. If the interrupter does not work at first, add more sulphuric acid through the funnel and press the wire down a little more into the liquid. A piece of wood, A, Fig. 2, should be inserted in vibrator to prevent it from working.

Contributed by Harold L. Jones, Carthage, N. Y.

Construction of the "Pepper's Ghost" Illusion

Probably many readers have seen a "Pepper's Ghost" illusion at some amusement place. As there shown, the audience is generally seated in a dark room at the end of which there is a stage with black hangings. One of the audience is invited onto the stage, where he is placed in an upright open coffin. A white shroud is thrown over his body, and his clothes and flesh gradually fade away till nothing but his skeleton remains, which immediately begins to dance a horrible rattling jig. The skeleton then fades away and the man is restored again.

A simple explanation is given in the Model Engineer. Between the audience and the coffin is a sheet of transparent glass, inclined at an angle so as to reflect objects located behind the scenes, but so clear as to be invisible to the audience and the man in the coffin. At the beginning the stage is lighted only from behind the glass. Hence the coffin and its occupant are seen through the glass very plainly. The lights in front of the glass (behind the scenes) are now raised very gradually as those behind the glass are turned down, until it is dark there. The perfectly black surface behind the glass now acts like the silver backing for a mirror, and the object upon which the light is now turned—in this case the skeleton—is reflected in the glass, appearing to the audience as if really occupying the stage.

The model, which requires no special skill except that of carpentry, is constructed as shown in the drawings.

The box containing the stage should be 14 in. by 7 in. by 7-1/2 in., inside dimensions. The box need not be made of particularly good wood, as the entire interior, with the exception of the glass, figures and lights, should be colored a dull black. This can well be done by painting with a solution of lampblack in turpentine. If everything is not black, especially the joints and background near A, the illusion will be spoiled.

The glass should be the clearest possible, and must be thoroughly cleansed. Its edges should nowhere be visible, and it should be free from scratches and imperfections. The figure A should be a doll about 4 in. high, dressed in brilliant, light-colored garments. The skeleton is made of papier maché, and can be bought at Japanese stores. It should preferably be one with arms suspended by small spiral springs, giving a limp, loose-jointed effect. The method of causing the skeleton to dance is shown in the front view. The figure is hung from the neck by a blackened stiff wire attached to the hammer wire of an electric bell, from which the gong has been removed. When the bell works he will kick against the rear wall, and wave his arms up and down, thus giving as realistic a dance as anyone, could expect from a skeleton.

The lights, L and M, should be miniature electric lamps, which can be run by three dry cells. They need to give a fairly strong light, especially L, which should have a conical tin reflector to increase its brilliancy and prevent its being reflected in the glass.

Since the stage should be some distance from the audience, to aid the illusion, the angle of the glass and the inclination of the doll, A, has been so designed that if the stage is placed on a mantle or other high shelf, the image of A will appear upright to an observer sitting in a chair some distance away, within the limits of an ordinary room. If it is desired to place the box lower down, other angles for the image and glass may be found necessary, but the proper tilt can be found readily by experiment.

The electric connections are so simple that they are not shown in the drawings. All that is necessary is a two-point switch, by which either L or M can be placed in circuit with the battery, and a press button in circuit with the bell and its cell. If a gradual transformation is desired, a double-pointed rheostat could be used, so that as one light dims the other increases in brilliancy, by the insertion and removal of resistance coils.

With a clear glass and a dark room this model has proved to be fully as bewildering as its prototype.

Two-Colored Hand

To many the following experiment may be much more easily performed than explained: Place the hand or other object in the light coming from two incandescent lamps, one red and one white, placed about a foot apart, and allow the shadow to fall on a white screen such as a table-cloth. Portions of the shadow will then appear to be a bright green. A similar experiment consists in first turning on the red light for about a minute and then turning it off at the same time that the white one is turned on. The entire screen will then appear to be a vivid green for about one second, after which it assumes its normal color.

A 1-in. hole was bored in the center of a 2-in. square block. Two finishing nails were driven in, as shown in the sketch. These were connected to terminals of an induction coil. After everything was ready the powder was poured in the hole and a board weighted with rocks placed over the block. When the button is pressed or the circuit closed in some other way the discharge occurs. The distance between the nail points—which must be bright and clean—should be just enough to give a good, fat spark.

Contributed by Geo. W. Fry, San Jose, Cal.

Simple Wireless System

The illustrations will make plain a simple and inexpensive apparatus for wireless telegraphy by which I have had no difficulty in sending messages across 1-1/2 miles of water surface. It is so simple that the cuts scarcely need explanation. In Fig. 1 is seen the sending apparatus, consisting of a 40-cell battery connected with two copper plates 36 by 36 by 1/8 in. The plates are separated 6 in. by a piece of hard rubber at each end.

In Fig. 2 are seen duplicates of these insulated plates, connected with an ordinary telephone receiver. With this receiver I can hear distinctly the electric signals made by closing and opening the Morse key in Fig. 1, and I believe that in a short time I shall be able to perfect this system so as to send wireless messages over long distances.

Contributed by Dudley H. Cohen, New York.

To prevent water colors from crawling, add a few drops of ammonia or lime water, or a solution of sal soda.

Hydrogen Generator

A small hydrogen generator may be made from a fruit jar, A (see sketch), with two tubes, B and C, soldered in the top. The plates E can be made of tin or galvanized iron, and should be separated about 1/8 in. by small pieces of wood. One of these plates is connected to metal top, and the wire from the other passes through the tube B, which is filled with melted rosin or wax, to make it airtight. This wire connects to one side of a battery of two cells, the other wire being soldered to the metal top of the jar, as shown. The jar is partly filled with a very dilute solution of sulphuric acid, about 1 part of acid to 20 of water.

When the current of electricity passes between the plates E, hydrogen gas is generated, which rises and passes through the rubber hose D, into the receiver G. This is a wide-mouth bottle, which is filled with water and inverted over a pan of water, F.

The gas bubbling up displaces the water and fills the bottle. If the receiver is removed when half full of gas, the remaining space will be filled with air, which will mix with the gas and form an explosive mixture. If a lighted match is then held near the mouth of the bottle a sharp report will be heard.

If the bottle is fitted with a cork containing two wires nearly touching, and the apparatus connected with an induction coil, in such a manner that a spark will be produced inside the bottle, the explosion will blowout the cork or possibly break the bottle. Caution should be used to avoid being struck by pieces of flying glass if this experiment is tried, and under no condition should a lighted match or spark be brought near the end of the rubber hose D, as the presence of a little air in the generator will make an explosive mixture which would probably break the jar.

Gasoline Burner

When making a small model traction engine or a locomotive the question arises, "What shall the fuel be?" If you have decided to use gasoline, then a suitable burner is necessary. A piece of brass tubing about 3 in. in diameter and 6 in. long with caps screwed on both ends and fitted with a filling plug and a bicycle valve makes a good gasoline supply tank, says the Model Engineer, London. The bicycle valve is used to give the tank an air pressure which forces the gasoline to the burner.

The burner is made from a piece of brass tube, A, as is shown in the illustration, 1/2 in. in diameter and 2-1/2 in. long, which is plugged up at both ends, one end being drilled and reamed out to 5/16 in. Three rows of holes 1/16 in. in diameter are drilled in the brass tube. One row is drilled to come directly on top, and the other two at about 45 degrees from the vertical. It is then fitted to a sheet steel base, B, by means of the clips, C C, Fig. 1. A piece of 1/8-in. copper pipe, P, is then coiled around the brass tube, A, which forms the vaporizing coil. This coil should have a diameter of only 1 in. One end of the copper tube is bent around so it will point directly into the reamed-out hole in the end of the brass tube, A. A nipple, N, is made by drilling a 1/8-in. hole halfway through a piece of brass and tapping to screw on the end of the 1/8-in. copper pipe. A 1/64-in. hole is then drilled through the remaining part of the nipple. The other end of the copper tube is connected to the supply tank. The distance between the nipple, N, and the ends of the tube, A, should be only 5/16 of an inch. Fig. 2 shows the end view.

A telephone receiver that will do good work may be built very cheaply as follows: For the case use an ordinary 1/2-lb. baking-powder box with a piece of heavy wire soldered on the inside, 1-5/16 in. from the bottom. For the magnet use a piece of round hardened steel about 3/8 in. in diameter and 1-1/4 in. long. If desired, a piece of an old round file may be used for the magnet core, which should be magnetized previous to assembling, either by passing a current of electricity around it, or by direct contact with another magnet. The steel core should be wound with about 250 ft. of No. 36 insulated wire, the ends of which should be soldered to a piece of lamp cord, passed through a hole in the bottom of the can and knotted inside to prevent pulling out.

A disk of thin sheet-iron, such as is used by photographers for tintypes (Ferrotype), should be cut to the diameter of the can, taking care not to bend the iron. The magnet should then be placed in the bottom of the can in an upright position and enough of a melted mixture of beeswax and resin poured in to hold it in position.

While the wax is still in a plastic condition the magnet should be located centrally and adjusted so that the end will be 1/16 in. or less below the level of the top of the copper ring. After the wax has hardened the disk is slipped in and fastened tightly by a ring of solder when the instrument is ready for use.

Process of Homemade Binding

An easy way to bind Popular Mechanics in volumes of six months each is to arrange the magazines in order and tie them securely both ways with a strong cord. It is well to put two or three sheets of tough white paper, cut to the size of the pages, at the front and back for fly leaves.

Clamp the whole in a vise or clamp with two strips of wood even with the back edges of the magazines. With a sharp saw cut a slit in the magazines and wood strips about 1/2 in. deep and slanting as shown at A and B, Fig. 1. Take two strips of stout cloth, about 8 or 10 in. long and as wide as the distance between the bottoms of the sawed slits. Lay these over the back edge of the pack and tie securely through the slits with a string thread—wrapping and tying several times (C, Fig. 2).

If you have access to a printer's paper knife, trim both ends and the front edge; this makes a much nicer book, but if the paper knife cannot be used, clamp the whole between two boards and saw off the edges, boards and all, smoothly, with a fine saw.

Cut four pieces of cardboard, 1/4 in. longer and 1/4 in. narrower than the magazines after they have been trimmed. Lay one piece of the board on the book and under the cloth strips. Use ordinary flour paste and paste the strips to the cardboard and then rub paste all over the top of the strips and the board. Rub paste over one side of another piece of board and put it on top of the first board and strips, pressing down firmly so that the strips are held securely between the two boards. Turn the book over and do the same with the other two boards.

After the paste has dried a few minutes take a piece of strong cloth, duck or linen, fold and cut it 1 in. larger all around than the book, leaving the folded edge uncut. Rub paste over one of the board backs and lay one end of the cloth on it, smoothing and creasing as shown at A, Fig. 3. Turn the book over and paste the other side. The back edges should have a good coat of paste and a strip of paper the width of the thickness of the pack pasted on before pasting the cloth to the second board back.

Cut off the corners and fold over the edges of the cloth, pasting them down (Fig. 4). Rub paste on one side of a fly leaf and press the back down on it. Turn the book over and paste a fly leaf to the other back after the edges of the cloth have been folded down. The backs must not be opened until the fly leaves are thoroughly dry. Trim and tuck in the ends of the strip at the back edge. When fixed this way your magazines make one of the most valuable volumes you can possibly add to your library of mechanical books.

Contributed by Joseph N. Parker, Bedford City, Va.

A simple acetylene-gas generator used by myself for several years when out on camping trips was made of a galvanized iron tank, without a head, 18 in. in diameter and 30 in. deep, B, as shown in the sketch. Another tank, A, is made the same depth as B, but its diameter is a little smaller, so that inverted it will just slip easily into the tank B. In the bottom, or rather the top now, of tank A is cut a hole, and a little can, D, is fitted in it and soldered. On top and over can D is soldered a large tin can screw. A rubber washer is fitted on this so that when the screw top, E, is turned on it, the joint will be gas tight. Another can, C, which will just slip inside the little can, is perforated with a number of holes. This can C is filled about half full of broken pieces of carbide and then placed in the little can D. A gas cock, H, is soldered onto tank A, as shown, from which the gas may be taken through a rubber tube. Fill tank B with water and set tank A into it. This will cause some air to be enclosed, which can be released by leaving the cock open until tank A settles down to the point where the water will begin to run in the perforations of the little tank. The water then comes in contact with the carbide and forms gas, which expands and stops the lowering of tank A. Then the cock must be closed and tubing attached. It is dangerous to attempt to strike a match to light a jet or the end of the cock while air is escaping and just as the first gas is being made. Wait until the tank is well raised up before doing this.

Contributed by James E. Noble, Toronto, Ont.

Annuciator and Wiring Diagram

When one electric bell is operated from two push-buttons it is impossible to tell which of the two push-buttons is being operated unless an annunciator or similar device is used. A very simple annunciator for indicating two numbers can be made from a small box, Fig. 1, with an electric-bell magnet, A, fastened in the bottom. The armature, B, is pivoted in the center by means of a small piece of wire and has an indicator or hand, C, which moves to either right or left, depending on which half of the magnet is magnetized. If the back armature, D, of the magnet is removed the moving armature will work better, as this will prevent the magnetism from acting on both ends of the armature.

The wiring diagram, Fig. 2, shows how the connections are to be made. If the pushbutton A is closed; the bell will ring and the pointer will point at 1, while the closing of the push-button B will ring the bell, and move the pointer to 2.

Contributed by H. S. Bott, Beverly, N. J.

Detail of Box Kite

As some of the readers of Amateur Mechanics may desire to build a box kite, a simple method of constructing one of the modern type is given in detail as follows: The sticks should be made of straight grained wood, which may be either spruce, basswood or white pine. The longitudinal corner spines, A A, should be 3/8 in. square by 42 in. long, and the four diagonal struts, B, should be 1/4 in. by 1/2 in., and about 26 in. long. Two cloth bands should be made to the exact dimensions given in the sketch and fastened to the four longitudinal sticks with 1 oz. tacks. It is well to mark the positions of the sticks on the cloth bands, either with a soft lead-pencil or crayon, in order to have the four sides of each band exactly equal. The ends of the bands should be lapped over at least 1/2 in. and sewed double to give extra strength, and the edges should be carefully hemmed, making the width, when finished, exactly 12 in. Probably the best cloth for this purpose is nainsook, although lonsdale cambric or lightweight percaline will answer nearly as well.

The diagonal struts, B, should be cut a little too long, so that they will be slightly bowed when put in position, thus holding the cloth out taut and flat. They should be tied together at the points of intersection and the ends should be wound with coarse harness maker's thread, as shown at C, to prevent splitting. The small guards, D, are nailed or glued to the longitudinal sticks to prevent the struts slipping out of position. Of course the ends of the struts could be fastened to the longitudinal strips if desired, but if made as described the kite may be readily taken apart and rolled up for convenience in carrying.

The bridle knots, E, are shown in detail at H and J. H is a square knot, which may be easily loosened and shifted to a different position on the bridle, thus adjusting the lengths of F and G. A bowline knot should be tied at J, as shown, to prevent slipping. If the kite is used in a light wind, loosen the square knot and shift nearer to G, thus shortening G and lengthening F, and if a strong wind is blowing, shift toward F, thereby lengthening G and making F shorter. In a very strong wind do not use the bridle, but fasten a string securely to the stick at K.

Contributed by Edw. E. Harbert, Chicago.

An experienced photographer uses blacklead [graphite] for grooves about a camera or holder. A small quantity is rubbed well into the grooves and on the edges of shutters, that refuse to slide easily, with gratifying results. Care must be taken to allow no dust to settle in the holders, however.

Simple Telegraph Line

By using the circuit shown in the sketch for short-distance telegraph lines, the extra switches and wiring found in many circuits are done away with. Closing either key will operate both sounders, and, as the resistance of the sounders is very high, the batteries do not run down for a long time.

Contributed by A. D. Stoddard, Clay Center, Kan.

Thermo Battery

A thermo battery, for producing electricity direct from heat, can be made of a wooden frame, A, with a number of nails, B, driven in the vertical piece and connected in series with heavy copper wires, C. The connections should all be soldered to give good results, as the voltage is very low and the resistance of an unsoldered joint would stop the current.

The heat may be supplied by an alcohol lamp or other device, and the current may then be detected by means, of a simple galvanometer consisting of a square spool of No. 14 or No. 16 single-covered wire, E, with a pocket compass, F, placed on top. Turn the spool in a north and south direction, or parallel with the compass needle. Then, when the nail heads are heated and the circuit completed, the needle will swing around it at right angles to the coils of wire. Applying ice or cold water to the nail heads will reverse the current.

Contributed by A. C. A., Chicago.

Electrical Attachment for Discharging Toy Cannon

A device for discharging a toy cannon by electricity can be easily made by using three or four dry batteries, a switch and a small induction coil capable of giving a 1/8-in. spark. Fasten a piece of wood, A, to the cannon, by means of machine screws or, if there are no trunnions on the cannon, the wood may be made in the shape of a ring and slipped on over the muzzle. The fuse hole of the cannon is counterbored as shown and a small hole is drilled at one side to receive a small piece of copper wire, E. The wood screw, C, nearly touches E and is connected to one binding post of the induction coil. The other binding post is connected with the wood screw, D, which conducts the current into the cannon, and also holds the pieces of wood, A and B, in position.

When the cannon is loaded, a small quantity of powder is placed in the counterbore, and the spark between C and E ignites this and discharges the cannon. A cannon may be fired from a distance in this way, and as there is no danger of any spark remaining after the current is shut off, it is safer than the ordinary cannon which is fired by means of a fuse.

Contributed by Henry Peck, Big Rapids, Mich.

Lock Operated by a Magnet

The illustration shows an automatic lock operated by electricity, requiring a strong magnet, but no weights or strings, which greatly simplifies the device over many others of the kind.

The weight of the long arm, L, is just a trifle greater than the combined weights of the short arms, A and S. The fulcrum of the lever is at C, where there is a staple. The lever swings on one arm of the staple and the other arm is so placed that when the lever is in an upright position, with the long arm at L', it will not fall because of its greater weight but stays in the position shown. The purpose of this is to leave the short arm, A, when in position at A', within the reach of the magnet. Arm L rests on an L-shaped hook, H; in this position the door is locked.

To unlock the door, press the button, B. The momentum acquired from the magnet by the short arms, A and S, is sufficient to move the long arm up to the position of L'. To lock the door, press the button and the momentum acquired from the magnet by the short arms, now at A' and S', is sufficient to move the long arm down from L' to the position at L.

Contributed by Benjamin Kubelsky, Chicago.

Direct-Connected Reverse

A simple reverse for small motors can be attached directly to the motor as shown in Fig. 1. Fig. 2 shows the construction of the reverse block: A is a strip of walnut 5/8 in. square and 3/8 in. thick with strips of brass or copper (BB) attached as shown. Holes (CC) are drilled for the wire connections and they must be flush with the surface of the block. A hole for a 1/2 in. screw is bored in the block. In Fig. 1, D is a thin strip of walnut or other dense, hard wood fitted to the binding posts of the brush holders, to receive the screw in the center.

Before putting the reverse block on the motor, remove all the connections between the lower binding posts and the brush holders and connect both ends of the field coil to the lower posts. Bend the strips BB (Fig. 2) to the proper position to make a wiping contact with the nuts holding the strip of wood D, Fig. 1. Put the screw in tight enough to make the block turn a little hard. Connect as shown in the illustration. To reverse, turn the block so the strips change connections and the motor will do the rest.

Contributed by Joseph B. Keil, Marion, Ohio.

Combination Ax and Ice Chisel

Fishing through the ice is great sport, but cutting the first holes preparatory to setting the lines is not always an easy task. The ice chisel here described will be found very handy, and may be made at very slight expense.

In the top of an old ax-head drill a 9/16-in. hole, and then tap it for a 3/8-in. gas-pipe, about 18 in. long. Thread the other end of the pipe, and screw on an old snow-shovel handle. When ready for use, screw the two pieces together and you have your chisel complete.

A short ax-handle may be included in the outfit. When the holes are finished and your lines set, unscrew the pipe from the head of the ax, put in the handle, and your ax is ready to cut the wood to keep your fire going.

Contributed by C. J. Rand, West Somerville, Mass.

Lamp Shade and Dumbbell

It would seem that the number of useful articles that can be made from pipes and fittings is unlimited. The sketch shows two more that may be added to the list. A and B are front and side views of a lamp-screen, and C is a dumbbell. The lamp shade is particularly useful for shading the eyes when reading or writing and, if enameled white on the concave side, makes an excellent reflector for drawing at night, or for microscopic work.

The standard and base, consisting of an ordinary pipe flange bushed down to receive the upright nipple, are enameled a jet black, and if the device is to be used on a polished table, a piece of felt should be glued to the bottom. A good way to hold the fan in the nipple is to use a small wedge.

The dumbbells are made of short pieces of 3/4-in. pipe with 1-2-in. couplings fastened to each end by pouring melted lead in the space between the pipes and the couplings. The appearance is greatly improved by enameling black, and if desired the handles may be covered with leather.

Contributed by C. E. Warren, M. D., North Easton, Mass.

Bending Cold Sealing-Wax

If a piece of sealing-wax is supported in a horizontal position by one end, as shown at A in the sketch, it will gradually bend to the shape indicated by the dotted lines B. To attempt bending it with the hands would result in breaking it unless a steady pressure were applied for a long time. This peculiar property is also found in ice.

Homemade Pottery Kiln

A small kiln for baking clay figures may be built at a cost of $1. The following shows the general plan of such a kiln which has stood the test of 200 firings, and which is good for any work requiring less than 1400° C.

Get an iron pail about 1 ft. high by 1 ft. across, with a cover. Any old pail which is thick enough will do, while a new one will cost about 80 cents. In the bottom of this cut a 2-in. round hole and close it with a cork or wood plug, A, Fig. 1, which shall project at least 2 in. inside the pail. Make a cylindrical core of wood, B, Fig. 1, 8 in. long and 8 in. across. Make a mixture of clay, 60%; sand, 15%; and graphite, 25%, kneading thoroughly in water to a good molding consistency. Line the pail, bottom and sides, with heavy paper and cover the core with same. Now pack the bottom of the pail thoroughly with a 2-in. layer of the clay mixture, and on it set the paper wrapped core, carefully centering it. The 2 in. of space between the core and the sides of the pail all around is to be filled with clay, C, as is shown in the sketch, using a little at a time and packing it very tight. In like manner make the cover of the kiln, cutting the hole a little smaller, about 1 in. At the edge or rim of the cover encircle a 2-in. strip of sheet iron, E, Fig. 2, to hold the clay mixture, C. Set aside for a few days until well dried.

While these are drying you may be making a muffle, if there is to be any glazing done. This is a clay cylinder (Fig. 3) with false top and bottom, in which the pottery to be glazed is protected from any smoke or dust. It is placed inside the kiln, setting on any convenient blocks which will place it midway. The walls of the muffle should be about 1/2 in. thick, and the dimensions should allow at least 1 in. of space all around for the passage of heat between it and the walls of the kiln. By the time the clay of the kiln is well dried, it will be found that it has all shrunk away from the iron about 3/8 in. After removing all the paper, pack this space-top, bottom and sides-with moist ground asbestos. If the cover of the pail has no rim, it may be fastened to the asbestos and clay lining by punching a few holes, passing wire nails through and clinching them. Fit all the parts together snugly, take out the plugs in the top and bottom, and your kiln is ready for business. The handle of the pail will be convenient for moving it about, and it can be set on three bricks or some more elaborate support, as dictated by fancy and expense.

The temperature required for baking earthenware is 1250°-1310°, C.; hotel china, 1330°; hard porcelain, 1390°-1410°. These temperatures can not be obtained in the above kiln by means of the ordinary Bunsen burner. If will be necessary either to buy the largest size Bunsen, or make one yourself, if you have the materials. If you can get a cone which can be screwed into an inch pipe, file the opening of the cone to 1/16 in. diameter, and jacket the whole with a 2-1/2-in. pipe. The flame end of this burner tube should be about 4-1/2 in. above the cone opening and should be covered with gauze to prevent flame from snapping back. When lighted, the point of the blue flame, which is the hottest part, should be just in the hole in the bottom of the kiln. Such a burner will be cheaply made and will furnish a kiln temperature of 1400 degrees, but it will burn a great deal of gas.

A plumber's torch of medium size will cost more in the beginning, but will be cheaper in operation. Whatever burner is used, the firing should be gradual, and with especial caution the first time. By experiment you will find that a higher temperature is obtained by placing a 1-in. pipe 2-ft. long over the lid hole as a chimney. It would be still more effective to get another iron pail, 2 in. wider than the kiln, and get a down draft by inverting it over the kiln at whatever height proves most suitable.

G. L. W.

Medical Induction Coil

The coil to be described is 3-1/2 in., full length of iron core, and 3/4 in. in diameter.

Procure a bundle of small iron wire, say 1/4 in. in diameter, and cut it 3-1/2 in. long; bind neatly with coarse thread and file the ends smooth (Fig. 1). This done, make two wood ends, 1-1/4 by 1-1/4 in. and 3/8 in. thick, and varnish. Bore holes in the center of each so the core will fit in snugly and leave about 1/4 in. projecting from each end (Fig. 1).

After finishing the core, shellac two layers of thick paper over it between the ends; let this dry thoroughly. Wind two layers of bell magnet wire over this, allowing several inches of free wire to come through a hole in the end. Cover with paper and shellac as before.

Wind about 1/8 in. of fine wire, such as used on telephone generators, around the coil, leaving long terminals. Soak the whole in melted paraffin and let cool; bind tightly with black silk.

The vibrator is made of a piece of thin tin to which is soldered the head of an iron screw and on the other side a small piece of platinum, which can be taken from an old electric bell (Fig. 2).

Of course, a regulator must be had for the vibrator; this can be accomplished by bending a stout piece of copper wire as shown. The connections and the base for setting up are shown in the figures.

Contributed by J. T. R., Washington, D. C.

Card Trick

The following mechanical card trick is easy to prepare and simple to perform:

First, procure a new deck, and divide it into two piles, one containing the red cards and the other the black ones, all cards facing the same way. Take the red cards, square them up and place in a vise. Then, with a plane, plane off the upper right hand corner and lower left hand corner, as in Fig. 1, about 1/16 in.

Then take the black cards, square them up, and plane off about 1/16 in. on the upper left hand corner and lower right hand corner, as in Fig. 2.

Next restore all the cards to one pack, taking care to have the first card red, the next black, and so on, every alternate card being the same color. Bend the pack so as to give some spring to the cards, and by holding one thumb on the upper left-hand corner all the cards will appear red to the audience; place thumb in the center at top of pack and they will appear mixed, red and black; with thumb on upper right-hand corner all cards appear black. You can display either color called for.

Contributed by Ralph Gingrich, Chicago.

Rain Gauge

An accurate rain gauge may be easily constructed from galvanized iron, as shown in the sketch herewith. The funnel, A, overlaps and rests on the body, B, and discharges into the tube, C, the area of which is one-tenth that of the top of the funnel. The depth of the water in C is thus ten times the actual rainfall, so that by measuring it with a stick marked off in tenths of an inch, we obtain the result in hundredths of an inch.

A good size to make the rain gauge is as follows: A, 8 in. diameter; C, 2.53 in.; length of C, about 20 in. It should be placed in an exposed location, so that no inaccuracy will occur from wind currents. To find the fall of snow, pour a known quantity of warm water on the snow contained in the funnel and deduct the quantity poured in from the total amount in the tube.

Contributed by Thurston Hendrickson, Long Branch, N.J.

Detail of Aquarium Frame

Aquarium Finished

In making an aquarium, the first thing to decide on is the size. It is well not to attempt building a very large one, as the difficulties increase with the size. A good size is 12 by 12 by 20 in., and this is inexpensive to build. First buy one length of 3/4 by 1/8-in. angle iron for the frame, F, Fig. 1. This can be obtained at any steel shop and should cost about 20 cents. All the horizontal pieces, B, should be beveled 45° at the ends and drilled for 3/16 in. stove bolts. The beveling may be done by roughing out with a hacksaw and finishing with a file. After all the pieces are cut and beveled they should be drilled at the ends for the 3/16-in. stove bolts, C. Drill all the horizontal pieces, B, first and then mark the holes on the upright pieces, A, through the holes already drilled, thus making all the holes coincide. Mark the ends of each piece with a figure or letter, so that when they are assembled, the same ends will come together again. The upright pieces, A, should be countersunk as shown in the detail, and then the frame is ready to assemble.

After the frame has been assembled take it to glazier and have a bottom made of skylight glass, and sides and ends of double-thick window glass. The bottom glass should be a good fit, but the sides and ends should be made slightly shorter to allow the cement, E, to form a dovetail joint as shown. When the glass is put in the frame a space, D, will be found between the glass and the horizontal pieces, B, of the frame. If this were allowed to remain the pressure of the water would spring the glass and cause a leak at E; so it is filled up with plaster of paris.

The cement, E, is made as follows: Take 1 gill of plaster of paris, 1 gill of litharge (lead monoxide), 1 gill of fine white sand, and 1/3 of a gill of finely powdered rosin. Mix well and add boiled linseed oil and turpentine until as thick as putty. Let the cement dry three or four days before putting any water in the aquarium.

In choosing stock for the aquarium it should be remembered that a sufficient quantity of vegetable life is required to furnish oxygen for the fish. In a well balanced aquarium the water requires renewal only two or three times a year. It is well to have an excess of plants and a number of snails, as the snails will devour all the decaying vegetable matter which would otherwise poison the water and kill the fish.

If desired, a centerpiece (A, Fig. 2) can be made of colored stones held together by cement, and an inverted jar can be supported in the position shown at B. If the mouth of the jar is below the surface of the water it will stay filled and allow the fish to swim up inside as shown. Some washed pebbles or gravel should be placed on the bottom, and, if desired, a few Chinese lilies or other plants may be placed on the centerpiece.

Pneumatic Door-Opener

Mount an old bicycle hand-pump, A, on the door by means of a metal plate, B, having a swinging connection at C. Fasten the lever, D, to the door knob, and make a hinge connection with the pump by means of a piece of sheet brass, E, soldered to the end of the cylinder. All this apparatus is on the inside of the door and is connected by a small rubber tube, F, to a secret mouthpiece placed at some convenient location. A small piece of spring brass, screwed to the door frame, will open the door about 1/2 in. when the operator blows in the mouthpiece, or if the door is within reach of the mouthpiece, the operator may push the door at the same time that he blows, thus doing away with the spring, which is only used to keep the door from relocking.

One way of making the air connection with the outside is to bend the tube F around and stick it through the keyhole. Few burglars would ever think to blow in the keyhole.

Contributed by Orton E. White, Buffalo, N. Y.

Detail of Homemade Waterwheel

In these days of modern improvements, most houses are equipped with a washing machine, and the question that arises in the mind of the householder is how to furnish the power to run it economically. I referred this question to my husband, with the result that he built a motor which proved so very satisfactory that I prevailed upon him to give the readers of Amateur Mechanics a description of it, hoping it may solve the same question for them.

A motor of this type will develop about 1/2 hp. with a water pressure of 70 lb. The power developed is correspondingly increased or decreased as the pressure exceeds or falls below this. In the latter case the power may be increased by using a smaller pulley. Fig. 1 is the motor with one side removed, showing the paddle-wheel in position; Fig. 2 is an end view; Fig. 3 shows one of the paddles, and Fig. 4 shows the method of shaping the paddles. To make the frame, several lengths of scantling 3 in. wide by 1 in. thick (preferably of hard wood) are required. Cut two of them 4 ft. long, to form the main supports of the frame, AA, Fig. 1; another, 2 ft. 6 in. long, for the top, B, Fig. 1; another, 26 in. long, to form the slanting part, C, Fig. 1; and another, D, approximately 1 ft., according to the slant given C. After nailing these together as shown in the illustration, nail two short strips on each side of the outlet, as at E, to keep the frame from spreading.

Cut two pieces 30 in. long. Lay these on the sides of the frame with their center lines along the line FF, which is 15 in. from the outside top of the frame. They are shown in Fig. 2 at GG. Do not fasten these boards now, but mark their position on the frame. Two short boards 1 in. wide by 1 in. thick (HH, Fig. 2) and another 1 in. by 1-1/2 in. (I, Fig. 2) form a substantial base.

Cut the wheel from sheet iron 1/16 in. thick, 24 in. in diameter. This can be done roughly with hammer and chisel and then smoothed up on an emery wheel, after which cut 24 radial slots 3/4 in. deep on its circumference by means of a hacksaw. On each side of the wheel at the center fasten a rectangular piece of 1/4-in. iron 3 by 4 in. and secure it to the wheel by means of four rivets; after which drill a 5/8 in. hole through the exact center of the wheel.

Cut 24 pieces of 1/32-in. iron, 1-1/2 by 2-1/2 in. These are the paddles. Shape them by placing one end over a section of 1-in. pipe, and hammer bowl shaped with the peen of a hammer, as shown in Fig. 4. Then cut them into the shape shown in Fig. 3 and bend the tapered end in along the lines JJ, after which place them in the slots of the wheel and bend the sides over to clamp the wheel. Drill 1/8-in. holes through the wheel and sides of the paddles and rivet paddles in place. Next secure a 5/8-in. steel shaft 12 in. long to the wheel about 8 in. from one end by means of a key. This is done by cutting a groove in the shaft and a corresponding groove in the wheel and fitting in a piece of metal in order to secure the wheel from turning independently of the shaft. Procure two collars or round pieces of brass (KK, Fig. 2) with a 5/8-in. hole through them, and fasten these to the shaft by means of set screws to prevent it from moving lengthwise.

Make the nozzle by taking a piece of 1/2-in. galvanized pipe 3-1/2 in. long and filling it with babbitt metal; then drill a 3/16-in. hole through its center. Make this hole conical, tapering from 3/16 in. to a full 1/2 in. This is best done by using a square taper reamer. Then place the nozzle in the position shown in Fig. 1, which allows the stream of water to strike the buckets full in the center when they reach the position farthest to the right.

Take the side pieces, GG, and drill a 1-in. hole through their sides centrally, and a 1/4-in. hole from the tops to the 1-in. holes. Fasten them in their proper position, with the wheel and shaft in place, the shaft projecting through the holes just mentioned. Now block the wheel; that is, fasten it by means of wedges or blocks of wood until the shaft is exactly in the center of the inch holes in the side pieces. Cut four disks of cardboard to slip over the shaft and large enough to cover the inch holes. Two of these are to be inside and two outside of the frames (one to bear against each side of each crosspiece). Fasten these to the crosspieces by means of tacks to hold them securely. Pour melted babbitt metal into the 1/4-in. hole to form the bearings. When it has cooled, remove the cardboard, take down the crosspieces, and drill a 1/8-in. hole from the top of the crosspieces through the babbitt for an oil-hole.

Secure sufficient sheet zinc to cover the sides of the frame. Cut the zinc to the same shape as the frame and let it extend down to the crosspieces EE. Tack one side on. (It is well to tack strips of heavy cloth—burlap will do—along the edges under the zinc to form a water-tight joint.) Fasten the crosspiece over the zinc in its proper position. Drill a hole through the zinc, using the hole in the crosspiece as a guide. Then put the wheel in a central position in the frame, tack the other side piece of zinc in place and put the other crosspiece in place. Place the two collars mentioned before on the shaft, and fasten so as to bear against the crosspieces, in order to prevent the wheel and shaft from moving sidewise. If the bearings are now oiled, the shaft should turn easily and smoothly. Fasten a pulley 4 or 6 in. in diameter to the longest arm of the shaft. Connect the nozzle to a water faucet by means of a piece of hose; place the outlet over a drain, and belt the motor direct to the washing-machine, sewing machine, ice-cream freezer, drill press, dynamo or any other machinery requiring not more than 1/2 hp.

This motor has been in use in our house for two years in all of the above ways, and has never once failed to give perfect satisfaction. It is obvious that, had the wheel and paddles been made of brass, it would be more durable, but as it would have cost several times as much, it is a question whether it would be more economical in the end. If sheet-iron is used, a coat of heavy paint would prevent rust and therefore prolong the life of the motor. The motor will soon pay for itself in the saving of laundry bills. We used to spend $1 a month to have just my husband's overalls done at the laundry, but now I put them in the machine, start the motor, and leave them for an hour or so. At the end of this time they are perfectly clean, and I have noticed that they wear twice as long as when I sent them to the laundry.

Making a Silhouette with the Camera

Photography in all branches is truly a most absorbing occupation. Each of us who has a camera is constantly experimenting, and everyone of us is delighted when something new is suggested for such experiments.

To use a camera in making silhouettes select a window facing north if possible, or if used only at times when the sun is not on it, any window will do, says the Photographic Times. Raise the window shade half way, remove any white curtains there may be, and in the center of the lower pane of glass paste by the four corners a sheet of tissue paper that is perfectly smooth and quite thick, as shown in the sketch at B. Darken the rest of the window, shutting out all light from above and the sides. Place a chair so that after being seated the head of the subject will come before the center of the tissue paper, and as near to it as possible, and when looking straight before him his face will be in clear profile to the camera.

Draw the shades of all other windows in the room. Focus the camera carefully, getting a sharp outline of the profile on the screen. Do not stop down the lens, as this makes long exposure necessary, and the subject may move.

Correct exposure depends, of course, on the lens, light and the plate. But remember that a black and white negative is wanted with as little detail in the features as possible. The best plate to use is a very slow one, or what is called a process plate.

In developing get all possible density in the high lights, without detail in the face, and without fog. Printing is best done on contrasty development paper with developer not too strong.

The ideal silhouette print is a perfectly black profile on a white ground. With a piece of black paper, any shape in stopping off print may be made as shown at C in the sketch.

Galvanoscope

Interior View

A galvanoscope for detecting small currents of electricity can be made from a coil of wire, A; a glass tube, B, full of water; a core, C; and a base, D, with binding posts as shown. The core C, which is made of iron and cork, is a trifle lighter than the water it displaces and will therefore normally remain in the top of the tube; but as soon as a current of electricity passes through the coil, the core is drawn down out of sight. The current required is very small, as the core is so nearly balanced that the least attraction will cause it to sink.

The glass tube may be a test tube, as shown in Fig. 2, or an empty developer tube. If one has neither a test tube nor developer tube, an empty pill bottle may be used. The washers at the ends of the coil can be made of fiber, hard rubber, or wood; or can be taken from an old magnet. The base may be made of wood or any other insulating material and should have four short legs on the bottom. Make the coil of single-covered wire about No. 18 and connect ends to binding posts as shown in Fig. 2.

The core is made by pushing a small nail through a piece of cork. It should be made so that it will rise slowly when placed under water. Some filing may be necessary to get the weight just right, but it should be remembered that the buoyancy of the core can be adjusted after the parts are assembled, by pressing the cork in the bottom of the test tube. This causes compression in the water so that some is forced into the upper cork, reducing its displacement and causing it to sink. The lower cork is then slowly withdrawn, by twisting, until the core slowly rises.

The instrument will then be adjusted ready for use.

Connect the binding posts to a single cell of battery—any kind will do, as a slight current will answer. On completing the circuit the core will descend; or put in a switch or push button on one of the battery wires. If the button be concealed where the operator can reach it, the core will obey his command to rise or fall, according to his control of the current. This is a mysterious looking instrument, the core being moved without visible connection to any other part.

To lubricate sheet metal mix 1 qt. whale oil, 1 lb. white lead, 1 pt. water and 3 oz. finest graphite. Apply with a brush before the metal enters the dies.

An Optical Top

One of the latest optical delusions, and one not easy to explain, is Benham's color top. Cut out the black and white disk shown in the figure, and paste on a piece of stiff cardboard. Trim the edges of the cardboard to match the shape of the disk, and make a pinhole in the center. Cut the pin in half and push it through from the under side until the head of the pin touches the cardboard. Spin slowly in a strong light and some of the lines will appear colored. The colors appear different to different people, and are changed by reversing the rotation.

Cards from a Tapered Deck

Another simple trick to perform but one not easily detected, is executed by using a tapered deck of cards as shown in Fig. 1. A cheap deck of cards is evened up square, fastened in a vise and planed along the edge in such a manner that all the pack will be tapered about 1/16 in. This taper is exaggerated in the illustration which shows one card that has been turned end for end.

It is evident that any card reversed in this way can be easily separated from the other cards in the pack, which makes it possible to perform the following trick: The performer spreads the cards out, fan-like, and asks an observer to withdraw a card, which is then replaced in any part of the pack. After thoroughly shuffling the cards the performer then holds the deck in both hands behind his back and pronouncing a few magic words, produces the card selected in one hand and the rest of the pack in the other. This is accomplished by simply turning the deck end for end while the observer is looking at his card, thus bringing the wide end of the selected card at the narrow end of the pack when it is replaced. The hands are placed behind the pack for a double purpose, as the feat then seems more marvelous and the observers are not allowed to see how it is done.

In prize games, players having the same score are frequently called upon to cut for low to determine which shall be the winner, but a fairer way is to cut for high as a person familiar with the trick shown in Fig. 2 can cut the cards at the ace, deuce, or three spot, nearly every time, especially if the deck is a new one. This is done by simply pressing on the top of the deck as shown, before cutting, thus causing the increased ink surface of the high cards to adhere to the adjacent ones. A little practice will soon enable one to cut low nearly every time, but the cards must be grasped lightly and the experiment should be performed with a new deck to obtain successful results.

Contributed by D.B.L., Chicago.

By fitting three bottles, A, B, C, with rubber stoppers and connecting with glass tubes as shown in the sketch, hydrogen or other gases produced in a similar manner may be generated under constant pressure. In making hydrogen, bottle B is partly filled with zinc nodules formed by slowly pouring melted zinc into water. Hydrochloric acid is then poured in the small funnel, thus partly filling bottles A and C. When the acid rising from C comes in contact with the zinc, hydrogen gas is generated and fills bottle B. The gas continues to generate until the pressure is sufficient to force the acid back down the tube into bottle C, when the action ceases. As fast as the gas is used the acid rises in the tube and generates more, thus keeping the pressure nearly constant, the pressure depending on the difference between the levels of the acid in bottle A and bottle B. As this device is easily upset, a ring-stand should be used to prevent its being broken, or if it is to be a permanent apparatus it may be mounted on a substantial wooden base. This apparatus may also be used for preparing acetylene gas or almost any gas which requires a mixture of a solid and liquid in its preparation.

Contributed by C. S. J., Detroit.

[Transcriber's note: I recall doing this experiment in a college chemistry lab. The instructor warned us to drape the experiment with a cloth before adding the acid. Ten minutes later there began a series of small explosions throughout the lab.]

Many a bell with a deadened tone due to a cracked rim, can be given its original clear ringing sound by sawing out the crack with a common hacksaw. Make the saw cut along the line of the crack. The opening caused by the saw will allow the free vibration of the metal.

Contributed by F. W. Bently, Jr., Huron, S. Dak.

Detail of Phonograph Horn

Secure a piece of tubing about 1-3/4 in. long that will fit the connection to the reproducer, and wrap a quantity of heavy thread around one end as shown in the enlarged sketch A, Fig. 1. Form a cone of heavy paper, 9 in. long and 3 in. in diameter, at the larger end with the smaller end to fit the diameter of the tube A, making it three-ply thick and gluing the layers together. Attach this cone on the tube A where the thread has been wrapped with glue, as shown in Fig. 2. Fig. 2 is also an enlarged sketch. Make ten pieces about 1 ft. 10 in. in length and 3 in. wide from the thin boards of a biscuit or cracker box. Cut an arc of a circle in them on a radius of 2 ft. (Fig. 3). Make a 10-sided stick, 12 in. long, that will fit loosely in the tube A, to which nail the 10 pieces as shown in Fig. 4, connecting the bottom by cross pieces, using care to keep them at equal distances apart and in a circle whose diameter is about 2 ft.

The cone is placed over the stick as shown by the dotted lines in Fig. 4 and temporarily fastened in position. Cut out paper sections (Fig. 5) that will cover each space between the 10 pieces, allowing 1 in. on one side and the top, in which to cut slits that will form pieces to overlap the next section and to attach with glue. Fasten the sections all around in like manner. The next course is put on in strips overlapping as shown at B, Fig. 6. Finish by putting on sections in the same way as the first course, making it three-ply thick. Remove the form, trim to suit and glue a piece of paper over the edge. When the glue is thoroughly hardened, put on two coats of white and one of blue paint, shading it to suit and striping it with gold bronze.

The Hygrometer

A homemade hygrometer, for determining the degree of moisture in the atmosphere, is shown in the accompanying sketch and consists of a board, A, with a nail at each end to hold the silk thread B. A second piece of silk thread, C, is tied to the center of B and connects with an indicating hand or pointer supported by the bracket D. The axle on which the pointer revolves consists of a piece of round wood, about the size of a lead-pencil, with a pin driven in each end. A piece of tin, E, is cut V-shaped at each end and bent up at the ends to form bearings for the pins. The silk thread C is fastened to the wooden axle and is wrapped one or two turns around it, so that when the thread is pulled the pointer will move on the scale. It will be noticed that the thread B is not perfectly straight, but bends toward D. For this reason a very small shrinkage of B, such as occurs when the atmosphere is dry, will cause an increased movement of C, which will be further increased in the movement of the pointer. An instrument of this kind is very interesting and costs nothing to make.

Contributed by Reader, Denver.

After shutting the front door and hearing the spring lock snap into its socket, most people go off with a childlike faith in the safety of their goods and chattels. But the cold fact is that there is scarcely any locking device which affords less protection than the ordinary spring lock. It is the simplest thing in the world for a sneak thief to slip a thin knife between the door-casing and the strip, push back the bolt, and walk in.

Fortunately, it is equally easy to block that trick. Take a narrow piece of tin 3 or 4 in. long, bend it at right angles throughout its length, and tack it firmly in the angle between the casing and strip, so as to make it impossible to reach the bolt without tearing off the strip.

Another way is to drive nails through the strip at intervals of half an inch, enough to protect the bolt from being meddled with.

Motor Reverse and Controller

Secure a cigar or starch box and use to make the base, B. Two wood-base switches, S S, are cut off a little past the center and fastened to the base with a piece of wood between them. The upper switch, S, is connected to different equal points on a coil of wire, W, while the lower switch, S, is connected each point to a battery, as shown. The reverse switch, R, is made from two brass or copper strips fastened at the top to the base with screws and joined together by a piece of hard rubber or wood with a small handle attached. Connect wires A to the armature and wires F to the field of the motor. By this arrangement one, two or three and so on up until all the battery cells are used and different points of resistance secured on the coil of wire. The reverse lever when moved from right to left, or left to right, changes the direction of the armature in the motor from one way to the other.

Contributed by J. Fremont Hilscher, Jr., West St. Paul, Minn.

Grape-Arbor Trellis

A grape arbor made of white pine, put together as shown in the sketch, will last for several years. The 2 by 4-in. posts, A, are 7 ft. long. The feet, B, are made 2 by 4 in., 4 ft. long, and rest on a brick placed under each end.

Toy Steam Engine Assembled

Valve Motion and Construction of Piston

Engine in Operation

A toy engine can be easily made from old implements which can be found in nearly every house.

The cylinder A, Fig. 1, is an old bicycle pump, cut in half. The steam chest D, is part of the piston tube of the same pump, the other parts being used for the bearing B, and the crank bearing C. The flywheel Q can be any small-sized iron wheel; either an old sewing-machine wheel, pulley wheel, or anything available. We used a wheel from an old high chair for our engine. If the bore in the wheel is too large for the shaft, it may be bushed with a piece of hard wood. The shaft is made of heavy steel wire, the size of the hole in the bearing B.

The base is made of wood, and has two wood blocks, H and K, 3/8 in. thick, to support bearing B, and valve crank S, which is made of tin. The hose E connects to the boiler, which will be described later. The clips FF are soldered to the cylinder and nailed to the base, and the bearing B is fastened by staples.

The valve motion is shown in Figs. 2 and 3. In Fig. 2 the steam is entering the cylinder, and in Fig. 3 the valve B has closed the steam inlet and opened the exhaust, thus allowing the steam in the cylinder to escape.

The piston is made of a stove bolt, E, Fig. 2, with two washers, FF, and a cylindrical piece of hard wood, G. This is wound with soft string, as shown in Fig. 3, and saturated with thick oil. A slot is cut in the end of the bolt E, to receive the connecting rod H. The valve B is made of an old bicycle spoke, C, with the nut cut in half and filed down as shown, the space between the two halves being filled with string and oiled.

The valve crank S, Fig. 1, is cut out of tin, or galvanized iron, and is moved by a small crank on the shaft. This crank should be at right angles to the main crank.

The boiler, Fig. 4, can be an old oil can, powder can, or a syrup can with a tube soldered to it, and is connected to the engine by a piece of rubber tubing. The heat from a small gas stove will furnish steam fast enough to run the engine at high speed.

This engine was built by W. G. Schuh and A. J. Eustice, of Cuba, Wis.

Electrolytic Writing

Soak a piece of white paper in a solution of potassium iodide and water for about a minute and then lay it on a piece of sheet metal. Connect the sheet metal with the negative or zinc side of a battery and then, using the positive wire as a pen, write your name or other inscription on the wet paper. The result will be brown lines on a white background.

Contributed by Geo. W. Fry, San Jose, Cal.

Neither a huge bottle nor a dwarfed man is necessary for this process, as it is merely a trick of photography, and a very amusing trick, at that.

First, photograph the person to be enclosed in the bottle against a dark plain background and mark the exact position on the ground glass. Let the exposure be just long enough to show the figure distinctly. Then place an empty bottle against a dark background and focus so as to have the outlines of the bottle enclose those of the man. Let this exposure be about twice the length of the first, and the desired result is obtained.

Make two wheels out of tin. They may be of any size, but wheel A must be larger than wheel B. On wheel A fasten two pieces of wood, C, to cross in the center, and place a bell on the four ends, as shown. The smaller wheel, B, must be separated from the other with a round piece of wood or an old spool. Tie four buttons with split rings to the smaller wheel, B. The blades on the wheels should be bent opposite on one wheel from the others so as to make the wheels turn in different directions. When turning, the buttons will strike the bells and make them ring constantly.

Move These Figures Rapidly with a Rinsing Motion

By giving the page a revolving or rinsing motion the three circular figures printed on the next page appear to rotate. The best effect will be produced by laying the book down flat on the desk or table and revolving, first in one direction and then in the opposite direction, in such a way that any given point on the page will describe a circle of about 1/2 in. diameter. Fig. 1 then appears to rotate in the same direction as the revolution; Fig. 2 appears to revolve in the opposite direction, and Fig. 3 appears to revolve sometimes in the same direction and at other times in the opposite direction.

A curious effect can be produced with Fig. 1 by covering up Figs. 2 and 3 with a piece of plain paper and laying a coin or other small object on the paper. If the vision is then concentrated on the coin or other object while same is being revolved, Fig. 1 will be seen to rotate.

Cheap and Comfortable

A hammock made of barrel staves is more comfortable than one would think, considering the nature of the material employed in making it. Good smooth staves should be selected for this purpose, and if one cares to go to little trouble a thorough sandpapering will make a great improvement. Cut half circles out of each stave, as shown at AA, and pass ropes around the ends as shown at B. When finished the weight will then be supported by four ropes at each end, which allows the use of small sized ropes, such as clothes lines. A hammock of this kind may be left out in the rain without injury.

Contributed by H.G.M., St. Louis, Mo.

To Make a Telephone Sing

Those who have not already tried the experiment may be interested to know that a telephone may be made to sing by holding the receiver about 1/16 in. from the transmitter, as shown in the illustration. The experiment will work well on most telephones, but not on all.

When the receiver is placed in the position shown it acts like an ordinary buzzer, and the function of the transmitter will then be that of an interrupter. The slightest movement of the transmitter diaphragm will cause an increased movement of the receiver diaphragm. This in turn will act on the transmitter, thus setting up sympathetic vibrations between the two, which accounts for the sound.

Detail of Lensless Microscope

Nearly everyone has heard of the pin-hole camera, but the fact that the same principle can be used to make a microscope, having a magnifying power of 8 diameters (64 times) will perhaps be new to some readers.

To make this lensless microscope, procure a wooden spool, A (a short spool, say 1/2 or 3/4 in. long, produces a higher magnifying power), and enlarge the bore a little at one end. Then blacken the inside with india ink and allow to dry. From a piece of thin transparent celluloid or mica, cut out a small disk, B, and fasten to the end having the enlarged bore, by means of brads. On the other end glue a piece of thin black cardboard, C, and at the center, D, make a small hole with the point of a fine needle. It is very important that the hole D should be very small, otherwise the image will be blurred.

To use this microscope, place a small object on the transparent disk, which may be moistened to make the object adhere, and look through the hole D. It is necessary to have a strong light to get good results and, as in all microscopes of any power, the object should be of a transparent nature.

The principle on which this instrument works is illustrated in Fig. 2. The apparent diameter of an object is inversely proportional to its distance from the eye, i. e., if the distance is reduced to one-half, the diameter will appear twice as large; if the distance is reduced to one-third, the diameter will appear three times as large, and so on. As the nearest distance at which the average person can see an object clearly is about 6 in., it follows that the diameter of an object 3/4 in. from the eye would appear 8 times the normal size. The object would then be magnified 8 diameters, or 64 times. (The area would appear 64 times as large.) But an object 3/4-in. from the eye appears so blurred that none of the details are discernible, and it is for this reason that the pin-hole is employed.

Viewed through this microscope, a fly's wing appears as large as a person's hand, held at arm's length, and has the general appearance shown in Fig. 3. The mother of vinegar examined in the same way is seen to be swarming with a mass of wriggling little worms, and may possibly cause the observer to abstain from all salads forever after. An innocent-looking drop of water, in which hay has been soaking for several days, reveals hundreds of little infusoria, darting across the field in every direction. These and hundreds of other interesting objects may be observed in this little instrument, which costs little or nothing to make.

Sounder-A, brass: B, wood: C, soft iron; DD, coils wound with No. 26 wire: E, nail soldered on A; FF, binding posts: H spring

KEY-A, wood; B, brass or iron soldered to nail; C, brass; D, brass: E, wood: F, connection of D to nail; HH, binding posts

The sounder, Fig. 1, is made from an old electric-bell magnet, D, fastened to a wooden base. The lever, A, can be made of brass and the armature, C, is made of iron. The pivot, E, is made from a wire nail and is soldered to A. It should be filed to a point at each end so as to move freely in the bearings, B, which are pieces of hard wood.

The spring, H, is fastened at each end by pins, bent as shown, and should not be too strong or the magnet will be unable to move the armature. The stop, K, is a wire nail driven deep enough in the base to leave about 1/8 in. between the armature and the magnet. The binding posts, F, may be taken from old dry batteries and are connected to the two wires from the magnet by wires run in grooves cut in the base.

The base of the key, Fig. 2, is also made of wood and has two wooden bearings, E, which are made to receive a pivot, similar to the one used in the sounder. The lever of the key is made of brass and has a hardwood knob, A, fastened near the end. A switch, D, connects with the pivot at F and can be either made from sheet brass, or taken from a small one-point switch. The binding posts are like those of the sounder, and are connected to the contacts, K, by wires run in grooves cut in the wood.

How to Make a Music Cabinet

A neat music cabinet can be made as shown in the accompanying sketch. Each side, AA, Fig. 1, is cut from a board about 36 in. in length and 16 in. wide. Both are alike and can be cut from the same pattern. As the front legs curve out a little the main body of the boards AA should be 15 in. wide. The back, B, should be about 22 in. long by 16 in. wide and set in between sides AA. Cut the top, C, 16 in. long and 14-1/4 in. wide. The bottom must be the same length as the top and 13-1/2 in. wide.

The door, D, can be made panel as shown, or a single piece, 16 in. wide and about 20 in. long. All material used is to be made from boards that will dress to 3/4 in. thick.

Shelving may be put in as shown in Fig. 2 and made from 1/4-in. material. Make 12 cleats, E, 13-1/2 in. long, from a strip of wood 1/2 by 3/4 in., with a groove 1/4 by 1/4 in. cut in them. Fasten 6 cleats evenly spaced on the inside of each of the sides, AA, with 3/4-in. brads. This will give seven spaces for music and as the shelves are removable two places can be made into one.

Detail of Coherer

A good wireless coherer may be made with very little expense, the only materials necessary being a glass tube, two corks: a magnetized needle and a quantity of iron and silver filings. Push a piece of wire through one cork and place in the bottom of the tube, as shown in the sketch.

Pour in the filings and insert the top cork with the needle pushed through from above. The point of the needle should barely touch the filings and by slightly agitating the tube the iron filings will separate from the silver and cling to the magnetized needle, as shown.

In operation, the device must stand on end and should be connected in the circuit as shown in the sketch. When the electrical waves strike the needle, the conductivity of the filings is established and a click is heard in the receiver.

Contributed by Carl Formhals, Garfield, Ill.

Diagram of One-Wire Line

The accompanying wiring diagram shows a telegraph system that requires no switches and may be operated with open-circuit batteries on a one-wire line with ground connections at each end. Any telegraph set in which the key makes double contact can be connected up in this way.

Contributed by R. A. Brown, Fairport, N. Y.

Water Rheostat

A water rheostat may be made by fitting a brass tube with a cork, through which a piece of wire is passed. The brass tube may be an old bicycle hand pump, A (see sketch), filled with water. Pushing the wire, B, down into the water increases the surface in contact, and thus decreases the resistance. An apparatus of this kind is suitable for regulating the current from an induction coil, when the coil is not provided with a regulator, and by using a piece of pipe instead of the tube, it can be used to regulate the speed of a motor.

When the pipe is used, a piece of brass or copper rod should be substituted for the wire, in order to increase the surface. Adding salt to the water will decrease the resistance, and, when used with a motor, will give a greater speed.

Contributed by John Koehler, Ridgewood, N. J.

Apparatus Placed on Inside of Door

Wiring Diagram

A very convenient and efficient device for unlocking any door fitted with a spring lock is shown in the accompanying sketches. A fairly stiff spring, A, is connected by a flexible wire cord to the knob B. The cord is also fastened to a lever, C, which is pivoted at D and is released by a magnetic trigger, E, made from the armature and magnet of an old electric bell.

When the circuit is completed by means of a secret contact device outside the door, the magnet, F, pulls down the armature, which releases the trigger and allows the spring to open the lock. If there are metal numbers on the outside of the door they may be used for the secret contact, if desired, but if there are no numbers on the door, a small contact-board may be constructed by driving about 12 brass headed tacks into a thin piece of wood and making connections at the back as shown in the wiring diagram.

In this particular diagram the tacks numbered 1 and 7 are used for unlocking the door, the others being connected with the electric-bell circuit as indicated, for the purpose of giving an alarm should anybody try to experiment with the secret contacts. By means of a pocket knife or other metal article the operator can let himself in at any time by connecting the tacks numbered 1 and 7, while a person not knowing the combination would be liable to sound the alarm. Of course, the builder of this device may choose a combination of his own and may thus prevent anybody else from entering the door, even those who read this description.

Contributed by Perry A. Borden, Gachville, N. B.

A common table fork can be used to hold the little projection on the end of a curtain roller for tightening the spring. Hold the fork firmly with one hand while turning the roller with the other. Do not let go of the fork until the little catches are set in position to prevent the spring from turning, or else the fork may be thrown off with dangerous force.

An automatic poultry feeder, which will discharge the necessary amount of corn or other feed at any desired time, may be made by using an alarm clock as shown in the sketch. A small wire trigger rests on the winding key and supports the swinging bottom of the food hopper by means of a piece of string which connects the two. When the alarm goes off the trigger drops and allows the door to open, thus discharging the contents of the hopper. After the device has been in operation for some time the hens will run to the feeder whenever the bell rings.

Contributed by Dr. H. A. Dobson, Washington, D. C.

Cabinet Holding 32 Records

Select some boards that have a nice grain and about 1 in. thick and 12-in. wide. Cut the end pieces each 36-in. long and trim down the edges so as to make them 11-3/8 in. wide. The top board is made 28-in. long and full 12-in. wide. The three shelves are cut 25-in. long and the edges trimmed so they will be 11-3/8 in. wide. The distance between the bottom of the top board and the top of the first shelf should be 3 in. Two drawers are fitted in this space, as shown in Fig. 1. A series of grooves are cut 1/4 in. wide, 1/4 in. deep and 3/4 in. apart on one side of the top and bottom shelves, as shown in Fig. 2, and on both sides of the middle shelf. The shelves should be spaced 9-5/8 in. for 10-in. records and 5-5/8 in. for 6-in. records. A neat scroll design is cut from a board 25 in. long to fill up and finish the space below the bottom shelf.

Contributed by H. E. Mangold, Compton, Cal.

Battery Rheostat

In a board 7 in. long and 5 in. wide bore holes about 1/4 in. apart, in a semicircle 2 in. from the bottom, and cut notches in top end to correspond with the holes. From a piece of brass a switch, C, is cut with a knob soldered on at the end. Nails for stops are placed at DD. Two binding-posts are placed in board at A and B. With about 9 ft. of fine iron wire attach one end to the bottom of post A and run through first hole and over in first notch to back of board and then through second hole and over second notch and so on until E is reached, where the other end of wire is fastened. Connect switch to post B.

Contributed by Edmund Kuhn, Jr., East Orange, N. J.

Will Open or Close Circuit as Desired

This device may be used to either open or close the circuit at any desired time. An alarm clock is firmly fastened to a wooden bracket and provided with a small wood or metal drum, A, to which is fastened a cord, B. The other end of the cord is tied to the switch handle so that when the alarm goes off the switch is either opened or closed, depending on whether the cord is passed over pulley C or pulley D.

When the cord is passed over pulley C, as shown in Fig. 1, the circuit will be closed when the alarm goes off, but if it is passed over D the circuit will be opened. Pulley D is fastened to a piece of spring steel, E, which in operation is bent, as shown by the dotted lines, thus causing the switch to snap open quickly and prevent forming an arc.

Contributed by Douglas Royer, Roanoke, Va.

Details of Rotary Pump

A simple rotary pump is constructed on the principle of creating a vacuum in a rubber tube and so causing water to rise to fill the vacuum. Figs. 3, 4 and 5 show all the parts needed, excepting the crank and tubing. The dimensions and description given are for a minimum pump, but a larger one could be built in proportion.

Through the center of a block of wood 4 in. square and 7/8 in. thick (A, Figs. 1, 2 and 3) saw a circular opening 2-7/8 in. in diameter. On each side of this block cut a larger circle 3-1/4 in. in diameter, having the same center as the first circle (Fig. 3). Cut the last circles only 1/4 in. deep, leaving the first circle in the form of a ridge or track 3/8 in. wide, against which the rubber tubing, E, is compressed by wheels. Bore two 1/4 in. holes (HH, Fig. 1) from the outside of the block to the edge of the inner circle. Put the rubber tube, E, through one of these holes, pass it around the track and out through the other hole. Notice the break (S) in the track; this is necessary in order to place in position the piece holding the wheels.

Fig. 4 shows the wheel-holder, B. Make it of hard wood 3-1/8 in. long, 1 in. wide and a little less than 7/8 in. thick, so that it will run freely between the sides (Fig. 5) when they are placed. Cut two grooves, one in each end, 1 in. deep and 1/2 in. wide. In these grooves place wheels, CC, to turn on pins of stout wire. These wheels should be 3/4 in. in diameter. When placed in the holder their centers must be exactly 2 in. apart, or so arranged that the distance between the edge of the wheels and the track (K, Fig. 1) is equal to the thickness of the tubing when pressed flat. If the wheels fit too tightly, they will bind; it too loose, they will let the air through. Bore a hole through the middle of the wheel-holder and insert the crankpin, D, which should be about 1/2 in. in diameter. The crankpin should fit tightly; if necessary drive a brad through to keep it from slipping.

In the sides (Fig. 5) bore a hole in the center of the crankpin to run in loosely. Now put all these parts together, as shown in the illustration. Do not fasten the sides too securely until you have tried the device and are sure it will run smoothly. For the crank a bent piece of stout wire or a nail will serve, though a small iron wheel is better, as it gives steadiness to the motion. In this case a handle must be attached to the rim of the wheel to serve as a crank. The drive wheel from a broken-down eggbeater will do nicely. For ease in handling the pump, a platform should be added.

To use the pump, fill the tube with water and place the lower end of the tube in a reservoir of water. Make a nozzle of the end of a clay pipe stem for the other end of the tube. Then turn the crank from left to right. The first wheel presses the air out of the tube, creating a vacuum which is immediately filled with water. Before the first wheel releases the tube at the top, the other wheel has reached the bottom, this time pressing along the water that was brought up by the first wheel. If the motion of the wheels is regular, the pump will give a steady stream. Two feet of 1/4-in. tubing, costing 10 cents, is all the expense necessary.

Contributed by Dan H. Hubbard, Idana, Kan.

Fig. 1
Fig. 2 Made of Strap Iron

A screen which will not interfere with the radiation of the heat from the fire, and will keep skirts and children safe can be made at little expense out of some strap iron. The screen which is shown in Fig. 1, stands 20 in. high from the base to the top cross-piece and is made of 3/4 by 1/4-in. and 1/2 by 1/4-in. iron. The top and bottom pieces marked AA, Fig. 1, are 3/4 by 1/4 in. and are 30 in. long, bent at an angle to fit the fireplace 7 in. from each end, as shown in Fig. 2. The three legs marked BBB, Fig. 1, are of the same size iron and each leg will take 34 in. of material. In shaping the feet of these three pieces give them a slight tendency to lean toward the fire or inside of screen, says a correspondent in the Blacksmith and Wheelwright. In the two cross bars 1 in. from each end, A in Fig. 2, mark for hole and 3 in. from that mark the next hole. Take the center of the bar, B, 15 in. from each end, and mark for a hole, and 3-1/2 in. on each side mark again and 3-1/2 in. beyond each of these two, mark again.

Mark the legs 2-3/4 in. from the bottom and 2 in. from the top and after making rivet-holes rivet them to the cross bars, AA, Fig. 1.

Cut six pieces, 17-1/2 in. long and punch holes to fit and rivet onto the remaining holes in cross bars, AA, Fig. 1. Clean it up and give it a coat of black Japan or dead black.

This is a box trap with glass sides and back, the panes of glass being held in place by brads placed on both sides. The animal does not fear to enter the box, because he can see through it: when he enters, however, and touches the bait the lid is released and, dropping, shuts him in. This is one of the easiest traps to build and is usually successful.

Fig.1 Details of Homemade Battery

Procure an ordinary carbon-zinc, sal-ammoniac battery and remove the zinc rod. If the battery has been used before, it is better to soak the carbon cylinder for a few hours to remove any remaining crystals of sal-ammoniac from its pores.

The truncated, conical zinc required is known as a fuller's zinc and can be bought at any electrical supply dealer's, or, it may be cast in a sand mold from scrap zinc or the worn-out zinc rods from sal-ammoniac batteries. It should be cast on the end of a piece of No. 14 copper wire. Amalgamation is not necessary for the zinc one buys, but if one casts his own zinc, it is necessary to amalgamate it or coat it with mercury. This may be done as follows:

Dip a piece of rag in a diluted solution of sulphuric acid (water 16 parts, acid 1 part); rub the zinc well, at the same time allowing a few drops of mercury to fall on a spot attacked by the acid. The mercury will adhere, and if the rubbing is continued so as to spread the mercury, it will cover the entire surface of the zinc, giving it a bright, silvery appearance.

Next procure what is known as a wire connector. This is a piece of copper tube about 1-1/2 in. long having two thumb screws, one on each end on opposite sides (Fig. 2). The upper screw is to connect the battery wire, the lower one to raise and lower the zinc. The battery is now complete, and the solution (Fig. 1) must be prepared. Proceed as follows:

In 32 oz. of water dissolve 4 oz. potassium bichromate. When the bichromate has all dissolved, add slowly, stirring constantly, 4 oz. sulphuric acid. Do not add the acid too quickly or the heat generated may break the vessel containing the solution. Then pour the solution into the battery jar, until it is within 3 in. of the top. Thread the wire holding the zinc through the porcelain insulator of the carbon cylinder and also through the wire connector. Pull the zinc up as far as it will go and tighten the lower thumb screw so that it holds the wire secure. Place the carbon in the jar. If the solution touches the zinc, some of it should be poured out. To determine whether or not the zinc is touched by the solution, take out the carbon and lower the zinc. If it is wet, there is too much liquid in the jar. The battery is now ready for use.

To cause a flow of electricity, lower the zinc until it almost touches the bottom of the jar and connect an electric bell or other electrical apparatus by means of wires to the two binding posts.

This battery when first set up gives a current of about two volts. It is useful for running induction coils, or small electric motors. When through using the battery, raise the zinc and tighten the lower thumb screw. This prevents the zinc wasting away when no current is being used.

Contributed by H. C. Meyer, Philadelphia.

Furnace Door Opener

The accompanying diagram shows an arrangement to open the coal door of a furnace. When approaching the furnace with a shovelful of coal it is usually necessary to rest the shovel on the top of the ash door, while the coal door is being opened. With my device it is only necessary to press the foot pedal, which opens the door. After putting in the coal, pressing the pedal closes the door. The pulley in the ceiling must be placed a little in front of the door, in order to throw the door open after lifting it from the catch. A large gate hinge is used to hold the pedal to the floor.

Contributed by Edward Whitney, Madison, Wis.

A simple but very efficient wireless telegraph may be constructed at slight cost from the following description:

The sending apparatus consists of nothing but an induction coil with a telegraph key inserted in the primary circuit, i. e., the battery circuit. This apparatus may be purchased from any electrical-supply house. The price of the coil depends upon its size, and upon the size depends the distance signals can be transmitted. If, however, one wishes to construct his own coil he can make and use, with slight changes, the jump-spark coil described elsewhere in this book. This coil, being a 1-in. coil, will transmit nicely up to a distance of one mile; while a 12-in. coil made on the same plan will transmit 20 miles or even more under favorable conditions.

Change the coil described, as follows: Insert an ordinary telegraph key in the battery circuit, and attach two small pieces of wire with a brass ball on each, by inserting them in the binding-posts of the coil as shown at B B". Of these two terminal wires one is grounded to earth, while the other wire is sent aloft and is called the aerial line. This constitutes all there is to the sending apparatus. Now for the receiving apparatus. In the earlier receiving instruments a coherer was used, consisting of a glass tube about 1/8-in. diameter, in which were two silver pistons separated by nickel and silver filings, in a partial vacuum. This receiver was difficult of adjustment and slow in transmission. An instrument much less complicated and inexpensive and which will work well can be made thus:

Take a 5-cp. incandescent lamp and break off the tip at the dotted line, as shown in Fig. 5. This can be done by giving the glass tip or point a quick blow with a file or other thin edged piece of metal. Then with a blow-torch heat the broken edges until red hot and turn the edges in as seen in Fig. 6. Remove the carbon filament in the lamp and bend the two small platinum wires so they will point at each other as in Fig. 6, W W. Screw the lamp into an ordinary wall socket which will serve as a base as in Fig. 7. Make a solution of 1 part sulphuric acid to 4 parts of water, and fill the lamp about two-thirds full (Fig. 7). This will make an excellent receiver. It will be necessary to adjust the platinum points, W W, to suit the distance the message is to be worked. For a mile or less the points should be about 1/16 in. apart, and closer for longer distances.

The tuning coil is simply a variable choking coil, made of No. 14 insulated copper wire wound on an iron core, as shown in Fig. 7. After winding, carefully scrape the insulation from one side of the coil, in a straight line from top to bottom, the full length of the coil, uncovering just enough to allow a good contact for the sliding piece. The tuning is done by sliding the contact piece, which is made of light copper wire, along the convolutions of the tuning coil until you can hear the signals. The signals are heard in a telephone receiver, which is shown connected in shunt across the binding posts of the lamp holder with one or two cells of dry battery in circuit, Fig.7.

The aerial line, No.6 stranded, is run from binding-post B through the choking or tuning coil, and for best results should extend up 50 ft. in the air. To work a 20-mile distance the line should be 100 or 150 ft. above the ground. A good way is to erect a wooden pole on a house or barn and carry the aerial wire to the top and out to the end of a gaff or arm.

To the end of the aerial wire fasten a bunch of endless loops made of about No. 14 magnet wire (bare or insulated), attaching both ends to the leading or aerial wire. The aerial wire should not come nearer than 1 ft. at any point to any metal which is grounded.

Run a wire from the other binding post, A, to the ground and be sure to make a good ground connection.

For simple experimental work on distances of 100 ft. only, an ordinary automobile spark coil can be used in place of the more elaborate coil, Figs. 1 to 4.

The above-mentioned instruments have no patents on them, and anyone is at liberty to build and use them. The writer does not claim to be the originator, but simply illustrates the above to show that, after all, wireless is very simple when it is once understood. The fundamental principles are that induction travels at right angles, 90°, to the direction of the current. For an illustration, if a person standing on a bridge should drop a pebble into the water below, after contact he would note circles radiating out over the surface of the water. These circles, being at right angles, 90°, to the direction of the force that caused the circles, are analogous to the flow of induction, and hence the aerial line, being vertical, transmits signals horizontally over the earth's surface.

When filling nail holes in yellow pine use beeswax instead of putty, as it matches the color well.

Assembled Lathe Bed and Bearing Details

FIG. 6 Headstock Details

FIG.7 Details of Tailstock

A small speed-lathe, suitable for turning wood or small metal articles, may be easily made at very little expense. A lathe of this kind is shown in the cut (Fig. 1), where A is the headstock, B the bed and C the tailstock. I run my lathe by power, using an electric motor and countershaft, but it could be run by foot power if desired. A large cone pulley would then be required, but this may be made in the same manner as the small one, which will be described later.

The bed of the machine is made of wood as shown in Figs. 2 and 3, hardwood being preferable for this purpose. Fig. 2 shows an end view of the assembled bed, and Fig. 3 shows how the ends are cut out to receive the side pieces.

The headstock, Fig. 6, is fastened to the bed by means of carriage bolts, A, which pass through a piece of wood, B, on the under side of the bed. The shaft is made of 3/4-in. steel tubing about 1/8 in. thick, and runs in babbitt bearings, one of which is shown in Fig. 5.

To make these bearings, cut a square hole in the wood as shown, making half of the square in each half of the bearing. Separate the two halves of the bearing slightly by placing a piece of cardboard on each side, just touching the shaft. The edges which touch the shaft should be notched like the teeth of a saw, so as to allow the babbitt to run into the lower half of the bearing. The notches for this purpose may be about 1/8 in. pitch and 1/8 in. deep. Place pieces of wood against the ends of the bearing as shown at A and B, Fig. 4, and drill a hole in the top of the bearing as shown in Fig. 4.

The bearing is then ready to be poured. Heat the babbitt well, but not hot enough to burn it, and it is well to have the shaft hot, too, so that the babbitt will not be chilled when it strikes the shaft. If the shaft is thoroughly chalked or smoked the babbitt will not stick to it. After pouring, remove the shaft and split the bearing with a round, tapered wooden pin. If the bearing has been properly made, it will split along the line of the notched cardboard where the section of the metal is smallest. Then drill a hole in the top as shown at A, Fig. 5, drilling just deep enough to have the point of the drill appear at the lower side. This cavity acts as an oil cup and prevents the bearing from running dry.

The bolts B (Fig. 5) are passed through holes in the wood and screwed into nuts C, which are let into holes D, the holes afterward being filled with melted lead. This type of bearing will be found very satisfactory and may be used to advantage on other machines. After the bearings are completed the cone pulley can be placed on the shaft. To make this pulley cut three circular pieces of wood to the dimensions given in Fig. 6 and fasten these together with nails and glue. If not perfectly true, they may be turned up after assembling, by rigging up a temporary toolrest in front of the headstock.

The tail stock (Fig. 7) is fastened to the bed in the same manner as the headstock, except that thumb nuts are used on the carriage bolts, thus allowing the tail stock to be shifted when necessary. The mechanism of the center holder is obtained by using a l/2-in. pipe, A, and a 1/2-in. lock nut, B, embedded in the wood.

I found that a wooden tool-rest was not satisfactory, so I had to buy one, but they are inexpensive and much handier than homemade tool rest.

Contributed by Donald Reeves, Oak Park, Ill.

Showing Zinc Suspended

When the lower half of a battery zinc becomes eaten away the remaining part can be used again by suspending it from a wire as shown in the cut. Be sure and have a good connection at the zinc binding post and cover that with melted paraffin. This prevents corrosion, which would otherwise occur from the action of the sal ammoniac or other chemical. The wire may be held at the top by twisting it around a piece of wood or by driving a peg through the hole in the porcelain insulator.

Contributed by Louis Lauderbach, Newark, N.J.

Alarm Rings When Caller Approaches

This alarm rings so that callers approaching the door may be seen before they ring the bell and one can exercise his pleasure about admitting them.

If one has a wooden walk, the alarm is easy to fix up. Take up about 5 ft. of the walk and nail it together so as to make a trapdoor that will work easily. Place a small spring under one end to hold it up about 1/4 in. (A, Fig. 2). Nail a strip of tin along the under side of the trap near the spring and fasten another strip on the baseboard, so that they will not touch, save when a weight is on the trap. Connect up an electric bell, putting the batteries and bell anywhere desired, and using rubber-covered wire outside the house, and the alarm is complete.

When a person approaching the house steps on the trap, the bell will ring and those in the house can see who it is before the door bell rings.

Contributed by R. S. Jackson, Minneapolis, Minn.

Electroplating Apparatus

Before proceeding to electroplate with copper, silver or other metal, clean the articles thoroughly, as the least spot of grease or dirt will prevent the deposit from adhering. Then polish the articles and rub them over with a cloth and fine pumice powder, to roughen the surface slightly. Finally, to remove all traces of grease, dip the articles to be plated in a boiling potash solution made by dissolving 4 oz. American ash in 1-1/2 pt. of water. Do not touch the work with the hands again. To avoid touching it, hang the articles on the wires, by which they are to be suspended in the plating bath, before dipping them in the potash solution; then hold them by the wires under running water for ten minutes to completely remove every trace of the potash.

For plating with copper prepare the following solution: 4 oz. copper sulphate dissolved in 12 oz. water; add strong ammonia solution until no more green crystals are precipitated. Then add more ammonia and stir until the green crystals are redissolved giving an intense blue solution. Add slowly a strong solution of potassium cyanide until the blue color disappears, leaving a clear solution; add potassium cyanide again, about one-fourth as much in bulk as used in the decolorizing process. Then make the solution up to 2 qt. with water. With an electric pressure of 3.5 to 4 volts, this will give an even deposit of copper on the article being plated.

A solution for silver plating may be prepared as follows: Dissolve 3/4 oz. of commercial silver nitrate in 8 oz. of water, and slowly add a strong solution of potassium cyanide until no more white precipitate is thrown down. Then pour the liquid off and wash the precipitate carefully. This is best done by filling the bottle with water, shaking, allowing precipitate to settle and then pouring off the water. Repeat six times. Having finished washing the precipitate, slowly add to it a solution of potassium cyanide until all the precipitate is dissolved. Then add an excess of potassium cyanide—about as much as was used in dissolving the precipitate—and make the solution up to 1 qt. with water. This solution, with an electric pressure of 2 to 4 volts, will give a good white coat of silver in twenty minutes to half-an-hour; use 2 volts for large articles, and 4 volts for very small ones. If more solution is required, it is only necessary to double all given quantities.

Before silver plating, such metals as iron, lead, pewter, zinc, must be coated with copper in the alkaline copper bath described, and then treated as copper. On brass, copper, German silver, nickel and such metals, silver can be plated direct. The deposit of silver will be dull and must be polished. The best method is to use a revolving scratch brush; if one does not possess a buffing machine, a hand scratch brush is good. Take quick, light strokes. Polish the articles finally with ordinary plate powder.

The sketch shows how to suspend the articles in the plating-bath. If accumulators are used, which is advised, be sure to connect the positive (or red) terminal to the piece of silver hanging in the bath, and the negative (or black) terminal to the article to be plated. Where Bunsen cells are used, the carbon terminal takes the place of the positive terminal of the accumulator.

Model Engineer.

Electric Lock for Sliding Door

The apparatus shown in Fig. 1 not only unlocks, but opens the door, also, by simply pressing the key in the keyhole.

In rigging it to a sliding door, the materials required are: Three flat pulleys, an old electric bell or buzzer, about 25 ft. of clothesline rope and some No. 18 wire. The wooden catch, A (Fig. 1), must be about 1 in. thick and 8 in. long; B should be of the same wood, 10 in. long, with the pivot 2 in. from the lower end. The wooden block C, which is held by catch B, Can be made of a 2-in. piece of broomstick. Drill a hole through the center of this block for the rope to pass through, and fasten it to the rope with a little tire tape.

When all this is set up, as shown in Fig. 1, make a key and keyhole. A 1/4 in. bolt or a large nail sharpened to a point, as at F, Fig. 3, will serve for the key. To provide the keyhole, saw a piece of wood, I, 1 in. thick by 3 in. square, and bore a hole to fit the key in the center. Make a somewhat larger block (E, Fig. 3) of thin wood with a 1/8-in. hole in its center. On one side of this block tack a piece of tin (K, Fig. 3) directly over the hole. Screw the two blocks together, being careful to bring the holes opposite each other. Then, when the point of the key touches the tin, and the larger part (F, Fig. 3) strikes the bent wire L, a circuit is completed; the buzzer knocks catch A (Fig. 1), which rises at the opposite end and allows catch B to fly forward and release the piece of broomstick C. The weight D then falls and jerks up the hook-lock M, which unlocks the door, and the heavier weight N immediately opens it.

Thus, with a switch as in Fig. 3, the door can only be opened by the person who has the key, for the circuit cannot be closed with an ordinary nail or wire. B, Fig. 2, shows catch B, Fig. 1, enlarged; O, Fig. 2, is the cut through which the rope runs; H, Fig. 1, is an elastic that snaps the catch back into place, and at G the wires run outside to the keyhole.

This arrangement is very convenient when one is carrying something in one hand and can only use the other. Closing the door winds up the apparatus again.

Contributed by E. H. Klipstein, 116 Prospect St., East Orange, New Jersey.

The Magic Cave

You are seated in a parlor at night, with the lights turned low. In front of you, between the parlor and the room back of it, is an upright square of brightly burning lights, surrounding a perfectly black space. The magician stands in front of this, in his shirt sleeves, and after a few words of introduction proceeds to show the wonders of his magic cave. Showing you plainly that both hands are empty, he points with one finger to the box, where immediately appears a small white china bowl. Holding his empty hand over this bowl, some oranges and apples drop from his empty hand into the bowl. He removes the bowl from the black box, or cave, and hands its contents round to the audience. Receiving the bowl again, he tosses it into the cave, but it never reaches the floor—it disappears in midair.

The illusions he shows you are too many to retail at length. Objects appear and disappear. Heavy metal objects, such as forks, spoons and jackknives, which have been shown to the audience and which can have no strings attached to them, fly about in the box at the will of the operator. One thing changes to another and back again, and black art reigns supreme.

Now all this "magic" is very simple and requires no more skill to prepare or execute than any clever boy or girl of fourteen may possess. It is based on the performance of the famous Hermann, and relies on a principle of optics for its success. To prepare such a magic cave, the requisites are a large soap box, a few simple tools, some black paint, some black cloth, and plenty of candles.

The box must be altered first. One end is removed, and a slit, one-third of the length from the remaining end, cut in one side. This slit should be as long as the width of the box and about five inches wide. On either side of the box, half way from open end to closed end, should be cut a hole, just large enough to comfortably admit a hand and arm.

Next, the box should be painted black both inside and out, and finally lined inside with black cloth. This lining must be done neatly-no folds must show and no heads of tacks. The interior must be a dead black. The box is painted black first so that the cloth used need not be very heavy; but if the cloth be sufficiently thick, no painting inside is required. The whole inside is to be cloth-lined, floor, top, sides and end.

Next, the illumination in front must be arranged. If you can have a plumber make you a square frame of gas-piping, with tiny holes all along it for the gas to escape and be lit, and connect this by means of a rubber tube to the gas in the house, so much the better; but a plentiful supply of short candles will do just as well, although a little more trouble. The candles must be close together and arranged on little brackets around the whole front of the "cave" (see small cut), and should have little pieces of bright tin behind them, to throw the light toward the audience. The whole function of these candles is to dazzle the eyes of the spectators, heighten the illusion, and prevent them seeing very far into the black box.

Finally, you must have an assistant, who must be provided with either black gloves or black bags to go over his hands and arms, and several black drop curtains, attached to sticks greater in length than the width of the box, which are let down through the slit in the top.

The audience room should have only low lights; the room where the cave is should be dark, and if you can drape portieres between two rooms around the box (which, of course, is on a table) so much the better.

The whole secret of the trick lies in the fact that if light be turned away from anything black, into the eyes of him who looks, the much fainter light reflected from the black surface will not affect the observer's eye. Consequently, if, when the exhibitor puts his hand in the cave, his confederate behind inserts his hand, covered with a black glove and holding a small bag of black cloth, in which are oranges and apples, and pours them from the bag into a dish, the audience sees the oranges and apples appear, but does not see the black arm and bag against the black background.

The dish appears by having been placed in position behind a black curtain, which is snatched swiftly away at the proper moment by the assistant. Any article thrown into the cave and caught by the black hand and concealed by a black cloth seems to disappear. Any object not too large can be made to "levitate" by the same means. A picture of anyone present may be made to change into a grinning skeleton by suddenly screening it with a dropped curtain, while another curtain is swiftly removed from over a pasteboard skeleton, which can be made to dance either by strings, or by the black veiled hand holding on to it from behind, and the skeleton can change to a white cat.

But illusions suggest themselves. There is no end to the effects which can be had from this simple apparatus, and if the operators are sufficiently well drilled the result is truly remarkable to the uninitiated. The illusion, as presented by Hermann, was identical with this, only he, of course, had a big stage, and people clothed in black to creep about and do his bidding, while here the power behind the throne is but a black-veiled hand and arm. It can be made even more complicated by having two assistants, one on each side of the box, and this is the reason why it was advised that two holes be cut. This enables an absolutely instantaneous change as one uncovers the object at the moment the second assistant covers and removes the other.

It is important that the assistants remain invisible throughout, and if portieres are impossible, a screen must be used. But any boy ingenious enough to follow these simple instructions will not need to be told that the whole success of the exhibition depends upon the absolute failure of the audience to understand that there is more than one concerned in bringing about the curious effects which are seen. The exhibitor should be a boy who can talk; a good "patter"—as the magicians call it—is often of more value than a whole host of mechanical effects and helpers. It is essential that the exhibitor and his confederate be well drilled, so that the latter can produce the proper effects at the proper cue from the former. Finally, never give an exhibition with the "cave" until you have watched the illusions from the front yourself; so that you can determine whether everything connected with the draping is right, or whether some stray bit of light reveals what you wish to conceal.

Fig. 2 Suitable for Students' Use

A homemade reversing-switch, suitable for use by students of electrical and engineering courses in performing experiments, is shown in the diagram.

Referring to Fig. 1, A represents a pine board 4 in. by 4 in. and a is a circular piece of wood about 1/4 in. square, with three brass strips, b1, b2, b3, held down on it by two terminals, or binding posts, c1, c2, and a common screw, d. Post c1 is connected to d by means of an insulated wire, making them carry the same kind of current (+ in the sketch).

About the center piece H moves a disk, held down by another disk F (Fig. 2), which is fastened through the center piece to the wooden base, A, by means of two wood screws. On the disk G are two brass strips, e1 and e2, so arranged that, when handle K is turned to one side, their one end just slips under the strips b1, b2, or b2, b3, respectively, making contact with them, as shown in Fig. 2, at L, while their other ends slide in two half-circular brass plates f1, f2, held down on disk F by two other terminals, c3, c4, making contact with them as shown at y, Fig. 2.

The action of the switch is shown in Fig. 1. Connect terminal c1 to the carbon of a battery, and c2 to the zinc. Then, if you turn handle K to the right, so that the strips e1 and e2 touch b1 and b2, respectively, terminal c3 will show +, and c1 - electricity; vice versa, if you turn the handle to the left so that e1 and e2 touch b2 and b3, respectively, terminal c3 will show - , and c4 + electricity. The switch is easy to make and of very neat appearance.

Wiring Diagram for Wireless Telegraph

Any telephone having carbon in the transmitter (all ordinary telephones have carbon transmitters) can be used to receive wireless messages by simply making a few changes in the connections and providing a suitable antenna. Connect the transmitter and receiver in series with three dry cells and run one wire from the transmitter to the antenna. Connect the other transmitter wire to a water or gas pipe in order to ground it, and then hold the receiver to your ear. Any wireless telegraph message within a radius of one mile will cause the transmitter to act as a coherer, thus making the message audible in the receiver.

By using an ordinary telephone transmitter and receiver and a 1/2-in. jump spark coil, a complete wireless telegraph station may be made, which will send or receive messages for a radius of one mile. The accompanying wiring diagram shows how to make the connections. By putting in an extra switch three of the sending batteries may be switched in when receiving, thus obviating the necessity of an extra set of batteries.

Contributed by A. E. Joerin.

Referring to the illustration: A is a five-point switch (may be homemade); B is a one-point switch, and C and C1 are binding posts. When switch B is closed and A is on No. 1, you have the current of one battery; when A is on No. 2 you receive the current from two batteries; when on No. 3, from three batteries; when on No. 4, from four batteries, and when on No. 5, from five batteries. More batteries may be connected to each point of switch B.

I have been using the same method for my water rheostat (homemade). I have the jars of water where the batteries are and the current coming in at a and b.

Contributed by Eugene F. Tuttle, Jr., Newark, Ohio.

A simple accelerometer for indicating the increase in speed of a train was described by Mr. A. P. Trotter in a paper read before the Junior Institution of Engineers of Great Britain. The device consists of an ordinary 2-ft. rule, A, with a piece of thread tied to the 22-in. mark, as shown in the sketch, and supporting the small weight, B, which may be a button or other small object.

The device thus arranged, and placed on the windowsill of the car, will indicate the acceleration and retardation as follows: Every 1/2 in. traveled by the thread, over the bent portion of the rule, indicates an increase of or decrease of velocity to the extent of 1 ft. per second for each second. Thus, it the thread moved 2-1/4 in. in a direction opposite to the movement of the train, then the train would be increasing its speed at the rate of 4-1/2 ft. per second.

If the thread is tied at the 17-in. mark, then each half inch will represent the mile per hour increase for each second. Thus if the thread moves 1 in., it shows that the train is gaining 2 miles an hour each second.

Bottles having small necks are hard to fill without spilling the liquid. A funnel cannot be used in a small opening, and pouring with a graduate glass requires a steady hand. When you do not have a graduate at hand, a half egg-shell with a small hole pricked in the end will serve better than a funnel. Place the shell in an oven to brown the surface slightly and it will be less brittle and last much longer.

Contributed by Maurice Baudier, New Orleans, La.

Handy Electric Alarm

An electric alarm which one may turn off from the bed without arising combined with a light which may be turned on and off from a lying position, so one can see the time, is the device of H. E. Redmond, of Burlington, Wis.

The alarm clock rests on a shelf, A, which has a piece of metal, B, fastened in such a position that the metal rod C, soldered to the alarm winder, will complete the circuit and ring the bell. The two-point switch D is closed normally at E, but may be closed at F any time desired, thus turning on the small incandescent light G, which illuminates the face of the clock. When the alarm goes off, the bell will continue to ring until the switch is opened.

Last summer I was annoyed a great deal by dogs upsetting our garbage can on the lawn, but finally executed a plan that rid the yard of them in one afternoon.

I first secured a magneto out of an old telephone, then drove a spike in a damp place under the porch, attached a wire to the spike and ran the wire to one of the poles of the magneto. Then I set the garbage-can on some blocks of wood, being careful not to have it touch the ground at any point. I next ran a wire from the other pole of the magneto to the can, wrapping the wire around the can several times. Then I sat down on the porch to wait.

It was not long before a big greyhound came along, putting his forepaws on the top of the can to upset it. At the same instant I gave the magneto a quick turn, which sent the dog away a very surprised animal. This was repeated several times during the afternoon with other dogs, and with the same result.

Contributed by Gordon T. Lane, Crafton, Pa.

When crossing a water course on a fence rail or small log, do not face up or down the stream and walk sideways, for a wetting is the inevitable result. Instead, fix the eye on the opposite shore and walk steadily forward. Then if a mishap comes, you will fall with one leg and arm encircling the bridge.

C. C. S.

It is not necessary to remove the adjusting-screw when changing an electric bell into a relay. Simply twist it around as at A and bend the circuit-breaking contact back as shown. It may be necessary to remove the head of the screw, A, to prevent short-circuiting with the armature.

Contributed by A. L. Macey, New York City.

Fig. 1—Convenient Arrangement of Bench and Tools

Many amateur mechanics who require small metal castings in their work would like to make their own castings. This can easily be done at home without going to any great expense, and the variety and usefulness of the articles produced will make the equipment a good investment.

With the easily made devices about to be described, the young mechanic can make his own telegraph keys and sounders, battery zincs, binding posts, engines, cannons, bearings, small machinery parts, models and miniature objects, ornaments of various kinds, and duplicates of all these, and many other interesting and useful articles.

The first thing to make is a molding bench, as shown in Fig. 1. It is possible to make molds without a bench, but it is a mistake to try to do this, as the sand is sure to get on the floor, whence it is soon tracked into the house. The bench will also make the operation of molding much easier and will prove to be a great convenience.

The bench should be made of lumber about 1 in. thick and should be constructed in the form of a trough, as shown. Two cleats, AA, should be nailed to the front and back to support the cross-boards, BE, which in turn support the mold while it is being made. The object of using the cleats and removable cross-boards instead of a stationary shelf is to give access to the sand, C, when it is being prepared.

About one or two cubic feet of fine molding-sand will be required, which may, be purchased at the nearest foundry for a small sum. Yellow sand will be found a little better for the amateur's work than the black sand generally used in most foundries, but if no yellow sand can be obtained the black kind will do. If there is no foundry near at hand, try using sand from other sources, giving preference to the finest sand and that which clings together in a cake when compressed between the hands. Common lake or river sand is not suitable for the purpose, as it is too coarse and will not make a good mold.

For mixing and preparing the sand a small shovel, D, and a sieve, E, will be required. If desired the sieve may be homemade. Ordinary wire netting such as is used in screen doors, is about the right mesh, and this, nailed to replace the bottom of a box, makes a very good sieve.

The rammer, F, is made of wood, and is wedge-shaped at one end and flat at the other, as shown. In foundries each molder generally uses two rammers, but for the small work which will be described one will be sufficient. An old teaspoon, G, will be found useful in the molding operations and may be hung on the wall or other convenient place when not in use.

The cloth bag, H, which can be made of a knitted stocking, is filled with coal dust; which is used for a parting medium in making the molds. Take a small lump of soft coal and reduce to powder by pounding. Screen out all the coarse pieces and put the remainder in the bag. A slight shake of the bag over the mold will then cause a cloud of coal-dust to fall on it, thus preventing the two layers of sand from sticking, but this operation will be described more fully later on.

Fig. 2—Homemade Flask

The flask, J, Fig. 1, is shown more clearly in Fig. 2. It is made of wood and is in two halves, the "cope," or upper half, and the "drag," or lower part. A good way to make the flask is to take a box, say 12 in. by 8 in. by 6 in. high, and saw it in half longitudinally, as shown. If the box is not very strong, the corners should be braced with triangular wooden strips, A A, which should be nailed in, previous to sawing. The wooden strips BB are used to hold the sand, which would otherwise slide out of the flask when the two halves of the mold are separated.

The dowels, CC, are a very important part of the flask as upon them depends the matching of the two halves of the mold. A wedge-shaped piece, CC, is nailed to each end of the cope, and the lower pieces, DD, are then nailed on the drag so that they just touch C when the flask is closed. The two halves of the flask will then occupy exactly the same relative position whenever they are put together.

After the flask is done make two boards as shown at K, Fig. 1, a little larger than the outside of the flask. A couple of cleats nailed to each board will make it easier to pick up the mold when it is on the floor.

A cast-iron glue-pot makes a very good crucible for melting the metal, which can be either aluminum, white metal, zinc or any other metal having a low melting-point. This completes the equipment with the exception of one or two simple devices which will now be described.

Having finished making the flask and other equipment, as described, everything will be ready for the operation of molding. It would be well for those who have never had any experience in this line to visit a small brass foundry, where they can watch the molders at work, as it is much easier to learn by observation; but they must not expect to make a good mold at the first trial. The first attempt usually results in the sand dropping out of the cope when it is being lifted from the drag, either because of insufficient ramming around the edges or because the sand is too dry.

A good way to tell when the sand is moist enough is to squeeze it in the hand. If it forms into a cake and shows all the finger-marks, it has a sufficient amount of moisture, but if it crumbles or fails to cake it is too dry. An ordinary watering-pot will be found useful in moistening the sand, but care should be taken not to get it too wet, or the hot metal coming in contact with it when the mold is poured will cause such rapid evaporation that the mold will "boil" and make a poor casting. A little practice in this operation will soon enable the molder to determine the correct amount of moisture.

When molding with sand for the first time it will be necessary to screen it all before using it, in order to remove the lumps, and if water is added, the sand should be thoroughly shoveled until the moisture is evenly distributed. The sand is then ready for molding.

Fig. 3—Making a Mold

The operation of making a mold is as follows: The lower half of the flask, or "drag," and the pattern to be molded are both placed on the cover board as shown at A. A quantity of sand sufficient to completely cover the pattern is then sifted into the drag, which is then filled level with the top with unscreened sand. This is rammed down slightly with the rammer, and then more sand is added until it becomes heaped up as shown at B. It is then rammed again as before.

It is impossible to describe just how hard a mold should be rammed, but by observing the results the beginner can tell when a mold is too hard or too soft, and thus judge for himself. If the sand falls out of the flask when lifting the cope, or if it opens up or spreads after it is poured, it shows that the mold has been rammed too little, and if the surface of the sand next to the pattern is cracked it shows that the mold has been rammed too hard. It will be found that the edges of the mold can stand a little more ramming than the middle. In finishing the ramming, pound evenly all over the surface with the blunt end of the rammer.

After ramming, scrape off the surplus sand with a straight-edged stick, as shown at C, and scatter about 1/16 in. of loose sand over the surface for a good bearing. Place another cover board on top, as shown at D, and by grasping with both hands, as shown, turn the drag other side up. Remove the upper cover board and place the upper half of the flask, or "cope," in position, as shown at E.

In order to prevent the two layers of sand sticking together, the surface of the sand at E should be covered with coal-dust. This is done by shaking the coal-dust bag over the flask, after which the dust on the pattern may be removed by blowing. The cope is then filled with sand and rammed in exactly the same manner as in the case of the drag.

After the ramming is done a number of vent holes are made, as shown at F, from the surface of the mold to the pattern, in order to allow the escape of air and steam when the mold is being poured. These vent holes may be made by pushing a wire about the size of a knitting-needle down through the sand until it touches the pattern. The "sprue," or pouring-hole, is next cut, by means of the sprue-cutter shown at the right, which consists of a piece of thin brass or steel tubing about 3/4 in. in diameter.

Now comes the critical part of the molding operation—that of lifting the cope from the drag. It is here that the amateur often becomes discouraged, as the sand is liable to fall out of the cope and spoil the mold; but with a little practice and patience the molder can lift the cope every time without breaking it, as shown at G.

The next operation is that of cutting the gate, which carries the molten metal from the sprue to the opening left by the pattern. This is done with a spoon, a channel being cut about 3/4 in. wide and about 1/4 in. deep. The pattern is then drawn from the mold, as shown at H, by driving a sharp pointed steel rod into the pattern and lifting it from the sand. When a metal pattern is used a thread rod is used, which is screwed into a tapped hole in the pattern. Before drawing it is well to tap the drawing-rod lightly with another and larger rod, striking it in all directions and thus loosening the sand slightly from the pattern. Some molders tap the pattern gently when withdrawing, as shown at H, in order to loosen any sand which has a tendency to stick.

After drawing the pattern, place the cope back on the drag, as shown at J. Place a brick or other flat, heavy object on top of the mold above the pattern, to prevent the pressure of the melted metal separating the two halves of the mold, and then pour.

Having prepared one or more molds, the next operation is that of melting and pouring. An ordinary cast-iron glue-pot makes a good crucible and can be easily handled by a pair of tongs, made out of steel rod, as shown in the sketch. In order to hold the tongs together a small link can be slipped on over the handle, thus holding the crucible securely.

A second piece of steel rod bent in the form of a hook at the end is very useful for supporting the weight of the crucible and prevents spilling the molten metal should the tongs slip off the crucible. The hook is also useful for removing the crucible from the fire, which should be done soon after the metal is entirely melted, in order to prevent overheating. The metal should be poured into the mold in a small stream, to give the air a chance to escape, and should not be poured directly into the center of the opening, as the metal will then strike the bottom hard enough to loosen the sand, thus making a dirty casting.

Fig. 4—Pouring the Metal

If, after being poured, the mold sputters and emits large volumes of steam, it shows that the sand is too wet, and the castings in such cases will probably be imperfect and full of holes.

A mold made in the manner previously described may be poured with any desired metal, but a metal which is easily melted will give the least trouble. One of the easiest metals to melt and one which makes very attractive castings is pure tin. Tin melts at a temperature slightly above the melting point of solder, and, although somewhat expensive, the permanent brightness and silver-like appearance of the castings is very desirable. A good "white metal" may be made by mixing 75% tin, 15% lead, 5% zinc and 5% antimony. The object of adding antimony to an alloy is to prevent shrinkage when cooling.

A very economical alloy is made by melting up all the old type-metal, babbitt, battery zincs, white metal and other scrap available, and adding a little antimony if the metal shrinks too much in cooling. If a good furnace is available, aluminum can be melted without any difficulty, although this metal melts at a higher temperature than any of the metals previously mentioned.

In casting zincs for batteries a separate crucible, used only for zinc, is very desirable, as the presence of a very small amount of lead or other impurity will cause the batteries to polarize. A very good way to make the binding posts is to remove the binding posts from worn-out dry batteries and place them in the molds in such a way that the melted zinc will flow around them.

The time required for a casting to solidify varies with the size and shape of the casting, but unless the pattern is a very large one about five minutes will be ample time for it to set. The casting is then dumped out of the mold and the sand brushed off. The gate can be removed with either a cold chisel or a hacksaw, and the casting is then ready for finishing.

In cases where batteries are used in series and it is desirable to change the strength and direction of the current frequently, the following device will be found most convenient. In my own case I used four batteries, but any reasonable number may be used. Referring to the figure, it will be seen that by moving the switch A toward the left the current can be reduced from four batteries to none, and then by moving the switch B toward the right the current can be turned on in the opposite direction to the desired strength. In the various positions of these two switches the current from each individual cell, or from any adjacent pair of cells, may be used in either direction.

Contributed by Harold S. Morton, Minneapolis.

An Optical Illusion

The engraving shows a perfectly straight boxwood rule laid over a number of turned brass rings of various sizes. Although the effect in the illustration is less pronounced than it was in reality, it will be noticed that the rule appears to be bent, but sighting along the rule from one end will show that it is perfectly straight.

The brass rings also appear distorted. The portions on one side of the rule do not appear to be a continuation of those on the other, but that they really are can be proved by sighting in the same manner as before.

Contributed by Draughtsman, Chicago.

To perform this feat effectively the little device illustrated will be required. To make it take a sheet-iron band, A, 3/4 in. wide and attach a strap to fasten on the forearm between the wrist and elbow. Put a sharp needle point, B, through the sheet-iron so that it extends 3/4 in. outward. Make one of these pieces for each arm.

In lifting the table first show the hands unprepared to the audience and also a tight table, removing the cover to show that the surface of the table is not prepared in any way. Then replace the table, rest the hands upon it and at the same time press the needle points in the arm pieces into the wood of the table, which will be sufficient to hold it, says a correspondent of the Sphinx. Then walk down among the audience.

Paddle Boat in Operation

Detail of Paddle Boat

A rowboat has several disadvantages. The operation of the oars is both tiresome and uninteresting, and the oarsman is obliged to travel, backward. By replacing the oars with paddles, as shown in the illustration, the operator can see where he is going and enjoy the exercise much better than with oars. He can easily steer the boat with his feet, by means of a pivoted stick in the bottom of the boat, connected by cords to the rudder. At the blacksmith shop have a 5/8-in. shaft made, as shown at A, Fig. 2. It will be necessary to furnish a sketch giving all the dimensions of the shaft, which should be designed to suit the dimensions of the boat, taking care that sufficient clearance is allowed, so that the cranks in revolving will not strike the operator's knees. If desired, split-wood handles may be placed on the cranks, to prevent them from rubbing the hands.

The bearings, B, may be made of hardwood, but preferably of iron pipe filled with melted babbitt. If babbitt is used, either thoroughly smoke or chalk the shaft or wrap paper around it to prevent the babbitt sticking. The pieces of pipe may be then fastened to the boat by means of small pipe straps, such as may be obtained at any plumber's at a very small cost.

The hubs, C, should be made of wood, drilled to fit the shaft and mortised out to hold the paddles, D. The covers, E, may be constructed of thin wood or galvanized iron and should be braced by triangular boards, as shown in Fig. 1. If galvanized iron is used, it should be exposed to the weather two or three months before painting, or the paint will come off, spoiling its appearance.

Experiment with a Block of Ice

Of all the boys who make snowballs probably few know what occurs during the process. Under ordinary conditions water turns to ice when the temperature falls to 32°, but when in motion, or under pressure, much lower temperatures are required to make it a solid. In the same way, ice which is somewhat below the freezing point can be made liquid by applying pressure, and will remain liquid until the pressure is removed, when it will again return to its original state. Snow, being simply finely divided ice, becomes liquid in places when compressed by the hands, and when the pressure is removed the liquid portions solidify and unite all the particles in one mass. In extremely cold weather it is almost impossible to make a snowball, because a greater amount of pressure is then required to make the snow liquid.

This process of melting and freezing under different pressures and a constant temperature is well illustrated by the experiment shown in Figs. 1, 2 and 3. A block of ice, A, Fig. 1, is supported at each end by boxes BB, and a weight, W, is hung on a wire loop which passes around the ice as shown. The pressure of the wire will then melt the ice and allow the wire to sink down through the ice as shown in Fig. 2. The wire will continue to cut its way through the ice until it passes all the way through the piece, as shown in Fig. 3. This experiment not only illustrates how ice melts under pressure, but also how it solidifies when the pressure is removed, for the block will still be left in one piece after the wire has passed through.

Another peculiar property of ice is its tendency to flow. It may seem strange that ice should flow like water, but the glaciers of Switzerland and other countries are literally rivers of ice. The snow which accumulates on the mountains in vast quantities is turned to ice as a result of the enormous pressure caused by its own weight, and flows through the natural channels it has made in the rock until it reaches the valley below. In flowing through these channels it frequently passes around bends, and when two branches come together the bodies of ice unite the same as water would under the same conditions. The rate of flow is often very slow; sometimes only one or two feet a day, but, no matter how slow the motion may be, the large body of ice has to bend in moving.

This property of ice is hard to illustrate with the substance itself, but may be clearly shown by sealing-wax, which resembles ice in this respect. Any attempt to bend a piece of cold sealing-wax with the hands results in breaking it, but by placing it between books, as shown on page 65, or supporting it in some similar way, it will gradually change from the original shape A, and assume the shape shown at B.

Wiring Diagram

To use only one wire for a return call bell connect up as shown in the diagram, using a closed circuit or gravity battery, B. The current is flowing through both bells all the time, the same as the coils of a telegraph sounder, but is not strong enough to ring both connected in series. Pressing either push button, P, makes a short circuit of that bell and rings the one at the other end of the line.

Contributed by Gordon T. Lane, Crafton, Pa.

Interrupter for Induction Coil

Amateurs building induction coils are generally bothered by the vibrator contacts blackening, thus giving a high resistance contact, whenever there is any connection made at all. This trouble may be done away with by departing from the old single-contact vibrator and using one with self-cleaning contacts as shown. An old bell magnet is rewound full of No. 26 double cotton-covered wire and is mounted upon one end of a piece of thin sheet iron 1 in. by 5 in. as per sketch. To the other end of the strip of iron is soldered a piece of brass 1/64 in. by 1/4 in. by 2 in., on each end of which has been soldered a patch of platinum foil 1/4 in. square.

The whole is connected up and mounted on a baseboard as per sketch, the contact posts being of 1/16 in. by 1/2 in. brass, bent into shape and provided with platinum tipped thumb screws. The advantage of this style of an interrupter is that at each stroke there is a wiping effect at the heavy current contact which automatically cleans off any carbon deposit.

In the wiring diagram, A is the circuit breaker; B, the induction coil, and C, the battery.

Contributed by A. G. Ward, Wilkinsburg, Pa.

For a Summer Camp

Many of the Bulgarian peasants do their cooking in the open air over bonfires. The illustration shows a laborsaving machine in use which enables the cook to go away and leave meat roasting for an hour at a time. The illustration shows how the spit to which the meat is fastened is constantly turned by means of a slowly moving water wheel. Some of our readers may wish to try the scheme when camping out. The success depends upon a slow current, for a fast-turning wheel will burn the meat.

Wiring Diagram for Wireless Telegraph

The accompanying diagrams show a wireless-telegraph system that I have used successfully for signaling a distance of 3,000 ft. The transmitter consists of an induction coil, about the size used for automobiles, a key or push-button for completing the circuit, and five dry batteries. The small single-point switch is left open as shown when sending a message, but when receiving it should be closed in order that the electric waves from the antenna may pass through the coherer. The coherer in this case is simply two electric-light carbons sharpened to a wedge at one end with a needle connecting the two, as shown. An ordinary telephone receiver is connected in series with the coherer, as shown. To receive messages hold the receiver to the ear and close the switch, and answer by opening the switch and operating the key.

Contributed by Coulson Glick, Indianapolis.

Draft Regulator

A simple apparatus that will open the draft of the furnace at any hour desired is illustrated. The parts are: A, furnace; B, draft; C, draft chain; D, pulleys; E, wooden supports; F, vertical lever; G, horizontal lever; H, cord; I, alarm clock; J, weight. K shows where and how the draft is regulated during the day, the automatic device being used to open it early in the morning. The spool on the alarm clock is fastened to the alarm key by sawing a slit across the top of the spool and gluing it on. When the alarm goes off a cord is wound up on the spool and pulls the horizontal lever up, which releases the vertical lever and allows the weight to pull the draft open.

Contributed by Gordon Davis, Kalamazoo, Mich.

Artistic Window Boxes

During the winter months, where house plants are kept in the home, it is always a question how to arrange them so they can get the necessary light without occupying too much room.

The sketch shows how a neat window conservatory may be made at small cost that can be fastened on the house just covering a window, which will provide a fine place for the plants. The frame (Fig. 2) is made of about 2 by 2-in. material framed together as shown in Fig. 3. This frame should be made with the three openings of such a size that a four-paned sash, such as used for a storm window, will fit nicely in them. If the four vertical pieces that are shown in Fig. 2 are dressed to the right angle, then it will be easy to put on the finishing corner boards that hold the sash.

The top, as well as the bottom, is constructed with two small pieces like the rafters, on which is nailed the sheathing boards and then the shingles on top and the finishing boards on the bottom.

Simple Electroscope

An electroscope for detecting electrified bodies may be made out of a piece of note paper, a cork and a needle. Push the needle into the cork, and cut the paper in the shape of a small arrow. Balance the arrow on the needle as shown in the sketch, and the instrument will then be complete. If a piece of paper is then heated over a lamp or stove and rubbed with a piece of cloth or a small broom, the arrow will turn when the paper is brought near it.

Contributed by Wm. W. Grant, Halifax, N. S., Canada.

Fig. 1

Fig. 2

Producing electric light by means of small bulbs that give from one-half to six candle power, and a suitable source of power, is something that will interest the average American boy.

These circular bulbs range from 1/4 to 2 in. in diameter, and cost 27 cents each complete with base. They are commonly known as miniature battery bulbs, since a battery is the most popular source of power. The 1/2-cp. bulbs are usually 2-1/2 volts and take 1/4 ampere of current. It requires about three medium dry cells to operate it. However, there is now upon the market a battery consisting of 3 small dry cells connected in series, put up in a neat case with 2 binding posts, which sells for 25 cents. This is more economical than dry cells, as it gives about 4 volts and 3 amperes. It will run as large a lamp a 3-1/2 volts, 1 cp., for some time very satisfactorily. More than one lamp can be run by connecting the bulbs in parallel, as indicated by Fig. 1, which shows the special battery with 3 dry cells in the case, and the 2 binding posts for connection with the bulbs. In this case it is also advisable to connect several batteries in parallel also, so as to increase the current, but maintain the voltage constant. Thus the individual cells are in multiple series, i. e., multiples of series of three. By keeping in mind the ampere output of the battery and rating of the lamp, one can regulate the batteries as required. It must be remembered, in this connection, that any battery which is drawn upon for half of its output will last approximately three times as long, as if drawn upon for its total output. Thus, in any system of lamps, it is economical to provide twice as many batteries as necessary. This also supplies a means of still maintaining the candle power when the batteries are partially exhausted, by connecting them in series. However, this must be done with very great caution, as the lights will be burnt out if the voltage is too high.

Persons living in the city will find an economical means of lighting lamps by securing exhausted batteries from any garage, where they are glad to have them taken away. A certain number of these, after a rest, can be connected up in series, and will give the proper voltage.

In conclusion, for battery power: Connecting batteries in series increases the voltage, and slightly cuts down the current or amperage, which is the same as that of one battery; while connecting batteries in parallel increases the amperage, but holds the voltage the same as that of one cell. Thus, if the voltage and amperage of any cell be known, by the proper combination of these, we can secure the required voltage and amperage to light any miniature lamp. And it might be said that dry cells are the best for this purpose, especially those of low internal resistance.

For those having a good water supply there is a more economical means of maintenance, although the first cost is greater. Fig. 2 shows the scheme. A small dynamo driven by a water motor attached to a faucet, generates the power for the lights. The cost of the smallest outfit of the kind is about $3 for the water motor and $4 for the dynamo. This dynamo has an output of 12 watts, and will produce from 18 to 25 cp., according to the water pressure obtainable. It is advisable to install the outfit in the basement, where the water pressure is the greatest, and then lead No. 18 B & S. double insulated wire wherever needed. The dynamo can also be used as a motor, and is wound for any voltage up to ten. The winding should correspond to the voltage of the lamps which you desire to run. However, if wound for 6 volts, one could run parallel series of two 3-volt, 1-cp. lamps; making, as in Fig. 3, 11 series, or 22 lights. If wound for 10 volts, it would give 1-1/4 amperes and run four 6-cp. lamps. Thus, it will be seen that any candle power lamp can be operated by putting the proper number of lights in each series, and running the series in parallel. So, to secure light by this method, we simply turn on the water, and the water consumption is not so great as might be imagined.

Fig. 3

For the party who has electric light in his house there is still an easier solution for the problem of power. If the lighting circuit gives 110 volts he can connect eleven 10-volt lamps in series. These will give 3 cp. each, and the whole set of 11 will take one ampere of current, and cost about the same as a 32-cp. lamp, or 1-1/4 cents per hour. Simply connect the miniature circuit to an Edison plug, and insert in the nearest lamp socket. Any number of different candle power lamps can be used providing each lamp takes the same amount of current, and the sum of their voltages equals the voltage of the circuit used. This arrangement of small lights is used to produce a widely distributed, and diffused light in a room, for display of show cases, and for Christmas trees. Of all these sources of power the two last are the most economical, and the latter of these two has in its favor the small initial cost. These lamps are by no means playthings or experiments, but are as serviceable and practical as the larger lamps.

Contributed by Lindsay Eldridge, Chicago.

Anyone possessing a phonograph can try a very interesting and amusing experiment without going to any expense. Remove the belt and replace with a longer one, which can be made of narrow braid or a number of strands of yarn. The new belt should be long enough to allow crossing it, thus reversing the machine. This reverses every sound on the record and changes it to such an extent that very few words can be recognized.

The rack is made of any suitable kind of wood, and the sides, A, are cut just alike, or from one pattern. The shelves are made in various widths to fit the sides at the places where they are wanted. The number of shelves can be varied and to suit the size of the dishes. Cup hooks are placed on top and bottom shelves. It is hung on the wall the same as a picture from the molding.

Contributed by F. B. Emig, Santa Clara, Cal.

Reverse for a Small Motor

All that is necessary for reversing the motor is a pole-changing switch. Connect the two middle posts of the switch with each other and the two outside posts with each other. Then connect one of the outside posts of the switch to one brush of the motor and one middle post to the other brush.

Connect one bar of the switch to one end of the field coil and the other bar to one pole of the battery, and connect the other pole of the battery to the other field coil. To reverse the motor, simply change the switch.

Referring to the illustration, the letters indicate as follows: FF, field of motor; BB, brushes of motor; AA, bars of pole-changing switch; DD, center points of switch; CC, outside points of switch.

Contributed by Leonard E. Parker, Plymouth, Ind.

Shocking-Machine

The dogs in my neighborhood used to come around picking up scraps. After I connected up my induction coil, as shown in the sketch, we were not bothered with them. A indicates the ground; B, switch; and C, a bait of meat, or a tempting bone.

Contributed by Geo. W. Fry, 903 Vine St., San Jose, Cal.

Automatic Electric Lock for Doors

The illustration shows an automatic lock operated by electricity, one cell being sufficient. When the circuit is broken a weight, A, attached to the end of the armature B, tends to push the other end of the armature into the screw eye or hook C, which is in the door, thus locking the door.

To unlock the door, merely push the button E, The magnet then draws the armature out of the screw eye and the door is unlocked. The dotted line at D shows the position of the armature when the circuit is complete and the door unlocked. The weight must be in proportion to the strength of the magnet. If it is not, the door will not lock, or would remain locked. The button can be hidden, as it is the key to the lock.

Contributed by Claude B. Melchior, Hutchinson, Minn.

An Experiment in Equilibrium

An example of unstable equilibrium is shown in the accompanying sketch. All that is needed is a 2-foot rule, a hammer, a piece of string, and a table or bench. The experiment works best with a hammer having a light handle and a very heavy head. Tie the ends of the string together, forming a loop, and pass this around the hammer handle and rule. Then place the apparatus on the edge of the table, where it will remain suspended as shown.

Contributed by Geo. P. Schmidt, Culebra, Porto Rico, W. I.

Details of Reverser

On a block of hardwood draw a square (Fig. 1) and drill a hole in each corner of the square. Fill these holes with mercury and connect them to four binding posts (Fig. 1).

On another block of wood fasten two wires, as shown in Fig. 2, so that their ends can be placed in the holes in the first block. Then connect up with the motor and battery as in Fig. 3. When the block is placed on with the big arrow A pointing in the direction indicated in Fig. 3, the current flows with the small arrows. To reverse turn through an angle of 90 degrees (Fig. 4).

Contributed by F. Crawford Curry, Brockville, Ontario, Canada.

Automatic Time Draft-Opener

A stout cord, A, is attached to the draft B of the furnace, run through a pulley, C, in the ceiling and has a window weight, D, attached at the other end. A small stick is put through a loop in the cord at about the level of the table top on which the alarm clock F stands. The other end of stick E is placed under the key G of the alarm clock. When the alarm rings in the early morning, the key turns, the stick falls away, releasing the weight, which pulls the draft open.

Contributed by Edward Whitney, 18 Gorham St., Madison, Wis.

The Long-Distance Phonograph

An interesting experiment, and one calculated to mystify anyone not in the secret, is to transmit the music or speech from a phonograph to another part of the house or even a greater distance. For an outdoor summer party the music can be made to come from a bush, or tree, or from a bed of flowers. The apparatus is not difficult to construct.

The cut shows the arrangement. Procure a long-distance telephone transmitter, D, including the mouthpiece, and fasten it to the reproducer of the phonograph. Also a watch case receiver, R, which fasten to the horn. These parts may be purchased from any electrical-supply house. Connect two wires to the transmitter, running one direct to the receiver, and the other to the battery, thence to a switch, S, and then to the receiver. The more batteries used the louder will be the sound produced by the horn, but avoid using too much battery or the receiver is apt to heat.

Contributed by Wm. J. Farley, Jr., Camden, N. J.

Homemade Telescope

With a telescope like the one here described, made with his own hands, a farmer boy not many years ago discovered a comet which had escaped the watchful eyes of many astronomers. First, get two pieces of plate glass, 6 in. square and 1 in. thick, and break the corners off to make them round, grinding the rough edges on a grindstone. Use a barrel to work on, and fasten one glass on the top of it in the center by driving three small nails at the sides to hold it in place. Fasten, with pitch, a round 4-in. block of wood in the center on one side of the other glass to serve as a handle.

Use wet grain emery for coarse grinding. Take a pinch and spread it evenly on the glass which is on the barrel, then take the glass with the handle and move it back and forth across the lower glass, while walking around the barrel; also rotate the glass, which is necessary to make it grind evenly. The upper glass or speculum always becomes concave, and the under glass or tool convex.

Work with straight strokes 5 or 6 in. in length; after working 5 hours hold the speculum in the sunshine and throw the rays of the sun onto a paper; where the rays come to a point gives the focal length. If the glass is not ground enough to bring the rays to a point within 5 ft., the coarse grinding must be continued, unless a longer focal length is wanted.

Have ready six large dishes, then take 2 lb. flour emery and mix in 12 qt. of water; immediately turn the water into a clean dish and let settle 30 seconds; then turn it into another dish and let settle 2 minutes, then 8 minutes, 30 minutes and 90 minutes, being careful not to turn off the coarser emery which has settled. When dry, turn the emery from the 5 jars into 5 separate bottles, and label. Then take a little of the coarsest powder, wetting it to the consistency of cream, and spread on the glass, work as before (using short straight strokes 1-1/2 or 2 in.) until the holes in the glass left by the grain emery are ground out; next use the finer grades until the pits left by each coarser grade are ground out. When the two last grades are used shorten the strokes to less than 2 in. When done the glass should be semi-transparent, and is ready for polishing.

When polishing the speculum, paste a strip of paper 1-1/3 in. wide around the convex glass or tool, melt 1 lb. of pitch and turn on to it and press with the wet speculum. Mold the pitch while hot into squares of 1 in., with 1/4-in. spaces, as in Fig. 1. Then warm and press again with the speculum, being careful to have all the squares touch the speculum, or it will not polish evenly. Trim the paper from the edge with a sharp knife, and paint the squares separately with jeweler's rouge, wet till soft like paint. Use a binger to spread it on with. Work the speculum over the tool the same as when grinding, using straight strokes 2 in. or less.

Detail of Telescope Construction

When the glass is polished enough to reflect some light, it should be tested with the knife-edge test. In a dark room, set the speculum against the wall, and a large lamp, L, Fig. 2, twice the focal length away. Place a large sheet of pasteboard, A, Fig. 2, with a small needle hole opposite the blaze, by the side of the lamp, so the light from the blaze will shine onto the glass. Place the speculum S, Fig. 2, so the rays from the needle hole will be thrown to the left side of the lamp (facing the speculum), with the knife mounted in a block of wood and edgeways to the lamp, as in K, Fig. 2. The knife should not be more than 6 in. from the lamp. Now move the knife across the rays from left to right, and look at the speculum with the eye on the right side of the blade. When the focus is found, if the speculum is ground and polished evenly it will darken evenly over the surface as the knife shuts off the light from the needle hole. If not, the speculum will show some dark rings, or hills. If the glass seems to have a deep hollow in the center, shorter strokes should be used in polishing; if a hill in the center, longer strokes. The polishing and testing done, the speculum is ready to be silvered. Two glass or earthenware dishes, large enough to hold the speculum and 2 in. deep, must be procured. With pitch, cement a strip of board 8 in. long to the back of the speculum, and lay the speculum face down in one of the dishes; fill the dish with distilled water, and clean the face of the speculum with nitric acid, until the water will stick to it in an unbroken film.

The recipe for silvering the speculum is:

Mix solution D and make up to 25 fluid oz. with distilled water, pour into a bottle and carefully put away in a safe place for future use, as it works better when old:

Now take solution A and set aside in a small bottle one-tenth of it, and pour the rest into the empty dish; add the ammonia solution drop by drop; a dark brown precipitate will form and subside; stop adding ammonia solution as soon as the bath clears. Then add solution B, then ammonia until bath is clear. Now add enough of the solution A, that was set aside, to bring the bath to a warm saffron color without destroying its transparency. Then add 1 oz. of solution D and stir until bath grows dark. Place the speculum, face down, in the bath and leave until the silver rises, then raise the speculum and rinse with distilled water. The small flat mirror may be silvered the same way. When dry, the silver film may be polished with a piece of chamois skin, touched with rouge, the polishing being accomplished by means of a light spiral stroke.

Fig. 3 shows the position of the glasses in the tube, also how the rays R from a star are thrown to the eyepiece E in the side of the tube. Make the tube I of sheet iron, cover with paper and cloth, then paint to make a non-conductor of heat or cold. Make the mounting of good seasoned lumber.

Thus an excellent 6-in. telescope can be made at home, with an outlay of only a few dollars. My telescope is 64 in. long and cost me just $15, but I used all my spare time in one winter in making it. I first began studying the heavens through a spyglass, but an instrument such as I desired would cost $200—more than I could afford. Then I made the one described, with which I discovered a new comet not before observed by astronomers.

John E. Mellish.

Arrangement of Prisms

The "freak" pictures of well-known people which were used by some daily newspapers recently made everybody wonder how the distorted photographs were made. A writer in Camera Craft gives the secret, which proves to be easy of execution. The distortion is accomplished by the use of prisms, as follows: Secure from an optician or leaded-glass establishment, two glass prisms, slightly wider than the lens mount. The flatter they are the less they will distort. About 20. deg. is a satisfactory angle. Secure them as shown by the sectional sketch, using strawboard and black paper. Then make a ring to fit over the lens mount and connect it with the prisms in such a way as to exclude all light from the camera except that which passes through the face of the prisms. The inner surface of this hood must be dull black. The paper which comes around plates answers nicely. If the ring which slips over the lens mount is lined with black velvet, it will exclude all light and hold firmly to the mount, Place over lens, stop down well after focusing, and proceed as for any picture.

Simple Electric Lock

The details of the construction of an electrically operated lock are shown in the illustration. When the door is closed and the bolt A pushed into position, it automatically locks. To unlock, push the button D, which act will cause the electromagnet to raise the latch C, when the bolt may be drawn and the door opened.

Contributed by A. D. Zimmerman, Boody, Ill.

For the mixing of plaster of Paris for any purpose, add the plaster gradually to the water, instead of the contrary, says the Master Painter. Do not stir it, just sprinkle it in until you have a creamy mass without lumps. Equal parts of plaster and water is approximately the correct proportion. The addition of a little vinegar or glue water will retard the setting of the plaster, but will not preserve its hardening. Marshmallow powder also retards the setting. In this way the plaster may be handled a long time without getting hard. If you wish the plaster to set extra hard, then add a little sulphate of potash, or powdered alum.

Making Large Pictures with a Small Camera

Everyone who owns a hand camera has some pictures he would like enlarged. It is not necessary to have a large camera to do this, as the process is exceedingly simple to make large pictures from small negatives with the same hand camera.

A room from which all light may be excluded and a window through which the light can enter without obstruction from trees or nearby buildings, with a shelf to hold the camera and a table with an upright drawing-board attached, complete the arrangement. The back is taken out of the camera and fitted close against the back of the shelf, which must be provided with a hole the same size and shape as the opening in the back of the camera. The negative used to make the enlarged print is placed in the shelf at A, Fig. 1. The rays of the clear, unobstructed light strike the mirror, B, and reflect through the negative, A, through the lens of the camera and on the board, as shown in Fig. 2. The window must be darkened all around the shelf.

After placing the negative and focusing the lens for a clear image on the board, the shutter is set and a bromide paper is placed on the board. The paper is exposed, developed and fixed by the directions that are enclosed in the package of bromide papers.

Don't pull a lamp hung by flexible cord to one side with a wire and then fasten to a gas pipe. I have seen a wire become red hot in this manner. If the lamp hung by a cord must be pulled over, use a string.

Experiment with Spool and Card

Push a pin through an ordinary business card and place the card against one end of a spool with the pin inside the bore, as shown in the sketch. Then blow through the spool, and it will be found that the card will not be blown away, but will remain suspended without any visible support. This phenomenon is explained by the fact that the air radiates from the center at a velocity which is nearly constant, thereby producing a partial vacuum between the spool and the card. Can the reader devise a practical application of this contrivance?

Simple Current-Reversing Switch

Take two strips of copper or brass and fasten them together by means of gutta-percha (Fig. 1); also provide them with a handle. Saw out a rectangular block about one and one-half times as long as the brass strips and fasten to it at each end two forked pieces of copper or brass, as in Fig. 2. Fasten on the switch lever, as at A and B, Fig. 2, so that it can rotate about these points. Connect the wires as shown in Fig. 3. To reverse, throw the lever from one end of the block to the other.

Contributed by R. L. Thomas, San Marcos, Tex.

A Baitless Trap

A piece of an old bicycle tire and a glass fruit jar are the only materials required for making this trap. Push one end of the tire into the hole, making sure that there is a space left at the end so that the mice can get in. Then bend the other end down into a fruit jar or other glass jar. Bait may be placed in the jar if desired, although this is not necessary.

Contributed by Geo. G. McVicker, North Bend, Neb.

A brilliant polish may be given to tarnished nickel by immersing in alcohol and 2 per cent of sulphuric acid from 5 to 15 seconds. Take out, wash in running water, rinse in alcohol, and rub dry with linen cloth.

Arc Light

By rewinding an electric-bell magnet with No. 16 wire and connecting it in series with two electric-light carbons, as shown in the sketch, a small arc will be formed between the carbon points when the current is applied. In the sketch, A is the electric-bell magnet; B, the armature; C C, carbon sockets; D, carbons, and E E, binding posts. When connected with 10 or 12 dry batteries this lamp gives a fairly good light.

Contributed by Morris L. Levy, San Antonio, Tex.

Geissler Tube

An incandescent lamp of low candlepower may be illuminated by connecting to an induction coil in the manner shown in the sketch. One wire is connected to the metal cap of the lamp and the other wire is fastened to the glass tip. If the apparatus is then placed in the dark and the current turned on, a peculiar phosphorescent glow will fill the whole interior of the lamp. The induction coil used for this purpose should give a spark about 1/2 in. long or more.

Contributed by Joseph B. Bell, Brooklyn.

Jump-Spark Coil

The induction coil is probably the most popular piece of apparatus in the electrical laboratory, and particularly is it popular because of its use in experimental wireless telegraphy. Ten years ago wireless telegraphy was a dream of scientists; today it is the plaything of school-boys and thousands of grown-up boys as well.

Divested of nearly all technical phrases, an induction coil may be briefly described as a step-up transformer of small capacity. It comprises a core consisting of a cylindrical bundle of soft-iron wires cut to proper length. By means of two or more layers of No. 14 or No. 16 magnet wire, wound evenly about this core, the bundle becomes magnetized when the wire terminals are connected to a source of electricity.

Should we now slip over this electromagnet a paper tube upon which has been wound with regularity a great and continuous length of No. 36 magnet wire, it will be found that the lines of force emanating from the energized core penetrate the new coil-winding almost as though it were but a part of the surrounding air itself, and when the battery current is broken rapidly a second electrical current is said to be induced into the second coil or secondary.

All or any of the parts of an induction coil may be purchased ready-made, and the first thing to do is to decide which of the parts the amateur mechanic can make and which would be better to buy ready-made. If the builder has had no experience in coil-winding it would probably pay to purchase the secondary coil ready-wound, as the operation of winding a mile or more of fine wire is very difficult and tedious, and the results are often unsatisfactory. In ordering the secondary it is always necessary to specify the length of spark desired.

The following method of completing a 1-in. coil illustrates the general details of the work. The same methods and circuits apply to small and larger coils. The ready-made secondary is in solid cylindrical form, about 6 in. long and 2-5/8 in. diameter, with a hole through the winding 1-1/4 in. in diameter, as shown in Fig. 1. The secondary will stand considerable handling without fear of injury, and need not be set into a case until the primary is completed. The primary is made of fine annealed No. 24 iron wire cut 7 in. or 8 in. in length, as the maker prefers, and bundled to a diameter of 7/8 in. The wires may be straightened by rolling two or three at a time between two pieces of hard wood. If the amateur has difficulty in procuring this wire, the entire core may be purchased ready-made.

After the core wires are bundled, the core is wrapped with one or two layers of manila paper. The straighter the wire the more iron will enter into the construction of the core, which is desirable. Beginning half an inch from one end, No. 16 cotton-covered magnet wire is wound from one end to the other evenly and then returned, making two layers, and the terminals tied down to the core with twine. Core and primary are then immersed in boiling paraffine wax to which a small quantity of resin and beeswax has been added. This same wax may be used later in sealing the completed coil into a box. Over this primary is now wrapped one layer of okonite tape, or same thickness of heavily shellacked muslin. This completed primary will now allow of slipping into the hole in the secondary.

Should the secondary have been purchased without a case, a wooden box of mahogany or oak is made, large enough to contain the secondary and with an inch to spare all around, with room also for a small condenser; but if it is not convenient to do this work, a box like that shown in Fig. 2 may be purchased at a small cost. A 7/8-in. hole is bored in the center of one end, through which the primary core projects 1/8 in. This core is to be used to attract magnetically the iron head of a vibrating interrupter, which is an important factor of the coil. This interrupter is shaped as in Fig. 4, and is fastened to the box in such a way that the vibrator hammer plays in front of the core and also that soldered connections may be made inside the box with the screws used in affixing the vibrator parts to the box. The condenser is made of four strips of thin paper, 2 yd. long and 5 in. wide, and a sufficient quantity of tinfoil. When cut and laid in one continuous length, each piece of tin-foil must overlap the adjoining piece a half inch, so as to form a continuous electrical circuit. In shaping the condenser, one piece of the paper is laid down, then the strip of tin-foil, then two strips of paper and another layer of foil, and finally the fourth strip of paper. This makes a condenser which may be folded, beginning at one end and bending about 6 in. at a time. The condenser is next wrapped securely with bands of paper or tape, and boiled in pure paraffine wax for one hour, after which it is pressed under considerable weight until firm and hard. One of the sheets of tin-foil is to form one pole of the condenser, and the other sheet, which is insulated from the first, forms the other pole or terminal. (This condenser material is purchasable in long strips, ready for assembling.)

The wiring diagram, Fig. 3, shows how the connections are made. This method of connecting is suitable for all coils up to 1-1/2 in. spark, but for larger coil better results will be obtained by using an independent type of interrupter, in which a separate magnet is used to interrupt the circuit. Besides the magnetic vibrators there are several other types, such as the mercury dash-pot and rotary-commutator types, but these will become better known to the amateur as he proceeds in his work and becomes more experienced in coil operation.

This device consists of a battery and bell connection to an alarm clock which also acts as a door bell, the whole being mounted on a board 18 in. long and 12 in. wide.

Referring to the sketch accompanying this article, the letters indicate as follows: A, bell; B, battery ; C, switch; D, V-shaped copper strip; E, copper lever with 1-in. flange turned on one side, whole length, 4 in.; F, spring to throw lever E down in V-shaped piece to make connection; G, lever to hold out E when device is used as a door bell; lines H, go, one from bell, A, and one from battery, B, to the door; I, shelf for clock.

See that the ring in the alarm key of the clock works easily, so that when it is square across the clock it will drop down. Fasten a piece of copper about 1 in. long to key, then wind the alarm just enough so that the key stands straight up and down. Place the clock on the shelf and the key under the flange of lever E. Pull lever G down out of the way and close the lever on the switch. The alarm key will turn and drop down, letting lever E drop into the V-shaped piece D and make connection.

For the door-bell connection close lever on switch C, and put G up so that D and E do not come in contact. If anyone is ill and you do not want the bell to ring, open switch C.

The wiring for this device may all be on the back of the board. The switch and levers are fastened with small screw bolts, which allows wiring at the back. Saw two spools in half and fasten the halves to the four corners of the board at the back, and the apparatus may be put up where one likes.

Bend a piece of stout sheet iron 23 in. by 12 in. round so that the inside diameter is 7 in., and then rivet the seam. Fit in a round piece of sheet iron for the bottom. Make a hole about the size of a shilling in the side, 2 in. from the bottom. This is for blowing.

Line the furnace, bottom and sides with fire-clay to a depth of 1/2 in. Use charcoal to burn and an ordinary bellows for blowing, says the Model Engineer, London. The best blast is obtained by holding the nozzle of the bellows about an inch from the hole, instead of close to it.

Don't wrap paper around a lamp for a shade. You might go away and forget it and a fire might be started from the heat. Use a glass or metal shade. That is what they are for.

Setting Up a Gravity Battery

Many amateur electricians and some professionals have had considerable trouble with gravity batteries. They follow directions carefully and then fail to get good results. The usual trouble is not with the battery itself, but with the circuit. A gravity battery is suitable only for a circuit which is normally closed. It is therefore undesirable for electric bells, induction coils and all other open-circuit apparatus. The circuit should also have a high resistance. This makes it impractical for running fan motors, as the motor would have to be wound with fine wire and it would then require a large number of batteries to give a sufficiently high voltage.

To set up a gravity battery: Use about 3-1/2 lb. of blue stone, or enough to cover the copper element 1 in. Pour in water sufficient to cover the zinc 1/2 in. Short-circuit for three hours, and the battery is ready for use. If desired for use immediately, do not short-circuit, but add 5 or 6 oz. of zinc sulphate.

Keep the dividing line between the blue and white liquids about 1/2 in. below the bottom of the zinc. If too low, siphon off some of the white liquid and add the same amount of water, but do not agitate or mix the two solutions. This type of battery will give about 0.9 of a volt, and should be used on a circuit of about 100 milli-amperes.

How to Cut the Notches

In a recent issue of Popular Mechanics an article on "The Turning Card Puzzle" was described and illustrated. Outside of the scientific side involved, herein I describe a much better trick. About the time when the expression "skidoo" first began to be used I Invented the following trick and called it "Skidoo" and "Skidee," which created much merriment. Unless the trick is thoroughly understood, for some it will turn one way, for others the opposite way, while for others it will not revolve at all. One person whom I now recall became red in the face by shouting skidoo and skidee at it, but the thing would not move at all, and he finally from vexation threw the trick into the fire and a new one had to be made. Very few can make it turn both ways at will, and therein is the trick.

Take a piece of hardwood 3/8 in. square and about 9 in. long. On one of the edges cut a series of notches as indicated in Fig. 1. Then slightly taper the end marked B until it is nicely rounded as shown in Fig. 2. Next make an arm of a two-arm windmill such as boys make. Make a hole through the center of this one arm. Enlarge the hole slightly, enough to allow a common pin to hold the arm to the end B and not interfere with the revolving arm. Two or three of these arms may have to be made before one is secured that is of the exact proportions to catch the vibrations right.

To operate the trick, grip the stick firmly in one hand, and with the forward and backward motion of the other allow the first finger to slide along the top edge, the second finger along the side, and the thumb nail will then vibrate along the notches, thus making the arm revolve in one direction. To make the arm revolve in the opposite dlrection—keep the hand moving all the time, so the observer will not detect the change which the hand makes—allow the first finger to slide along the top, as in the other movement, the thumb and second finger changing places: e.g., In the first movement you scratch the notches with the thumb nail while the hand is going from the body, and in the second movement you scratch the notches with the nail of the second finger when the hand is coming toward the body, thus producing two different vibrations. In order to make it work perfectly (?) you must or course say "skidoo" when you begin the first movement, and then, no matter how fast the little arm is revolving when changed to the second movement you must say "skidee" and the arm will immediately stop and begin revolving in the opposite direction. By using the magic words the little arm will obey your commands instantly and your audience will be mystified. If any of your audience presume to dispute, or think they can do the same let them try it. You will no doubt be accused of blowing or drawing in your breath, and many other things in order to make the arm operate. At least it is amusing. Try it and see.

Contributed by Charles Clement Bradley, Toledo, Ohio.

Radium acts upon the chemical constituents of glass, porcelain and paper, imparting to them a violet tinge; changes white phosphorus to yellow, oxygen to ozone, affects photograph plates and produces many other curious chemical changes.

On its official trial trip the British torpedo boat destroyer "Mohawk" attained the record speed of a little over 39 miles an hour.

Magnified Nine Diameters

Usually the amateur photographer gets to a point in his work where the miscellaneous taking of everything in sight is somewhat unsatisfying: There are many special fields he may enter, and one of them is photomicrography. It is usually understood that this branch of photography means an expensive apparatus. If the worker is not after too high a magnification, however, there is a very simple and effective means of making photomicrographs which requires no additional apparatus that cannot be easily and quickly constructed at home.

Reproduced with this article is a photograph of dandelion seeds—a magnification of nine diameters or eighty-one times. The apparatus which produced this photograph consisted of a camera of fairly long draw, a means for holding it vertical, a short-focus lens, and, if possible, but not essential, a means for focusing that lens in a minute manner. On top of the tripod is the folding arrangement, which is easily constructed at home with two hinged boards, an old tripod screw, an old bed plate from a camera for the screw to fit in, and two sliding brass pieces with sets crews that may be purchased from any hardware store under the name of desk sliding braces. To the front board is attached a box, carrying the lens and the bed of the sliding object carrier, which can be moved forward and back by the rack and pinion, that also can be obtained from hardware stores. If the bed for the object carrier be attached to the bed of the camera instead of to the front board, the object carrier need have no independent movement of its own, focusing being done by the front and back focus of the camera; but this is less satisfactory, particularly when accurate dimensions are to be determined, says the Photographic Times. This outfit need not be confined to seeds alone, but small flowers, earth, chemicals, insects, and the thousand and one little things of daily life—all make beautiful subjects for enlarged photographs. These cannot be made by taking an ordinary photograph and enlarging through a lantern. When a gelatine dry plate is magnified nine diameters, the grains of silver in the negative will be magnified also and produce a result that will not stand close examination. Photographs made by photomicrography can be examined like any other photographs and show no more texture than will any print.

A steel pen makes an ideal substitute for a quill in the stopper of the draftsman's ink bottle. The advantage of this substitute is that there is always one handy to replace a broken or lost pen, while it is not so with the quill.

Contributed by George C. Madison, Boston, Mass.

Pattern for Cutting the Segments

Unusual interest is being displayed in ballooning, and as it is fast becoming the favorite sport many persons would like to know how to construct a miniature balloon for making experiments. The following table will give the size, as well as the capacity and lifting power of pilot balloons:

The material must be cut in suitable shaped gores or segments. In this article we shall confine ourselves to a 10-ft. balloon. If the balloon is 10 ft. in diameter, then the circumference will be approximately 3-1/7 times the diameter, or 31 ft. 5 in. We now take one-half this length to make the length of the gore, which is 15 ft. 7-1/2 in. Get a piece of paper 15 ft. 7-1/2 in. long and 3 ft. wide from which to cut a pattern, Fig. 1. A line, AB, is drawn lengthwise and exactly in the middle of the paper, and a line, CD, is drawn at right angles to AB and in the middle of the paper lengthways. The intersecting point of AB and CD is used for a center to ascribe a circle whose diameter is the same as the width of the paper, or 3 ft. Divide one-quarter of the circle into 10 equal parts and also divide one-half of the line AB in 10 equal parts. Perpendicular lines are drawn parallel with the line CD intersecting the division points made on the one-half line AB. Horizontal and parallel lines with AB are drawn intersecting the division points made on the one-quarter circle and intersecting the perpendicular line drawn parallel with CD. A line is now drawn from B to E and from E to F, and so on, until all the intersecting lines are touched and the point C is reached. This will form the proper curve to cut the pattern. The paper is now folded on the line AB and then on the line CD, keeping the marked part on the outside. The pattern is now cut, cutting all four quarters at the same time, on the curved line from B to C. When the paper is unfolded you will have a pattern as shown in Fig. 2. This pattern is used to mark the cloth, and after marked is cut the same shape and size.

Sewing Segments Together

The cloth segments are sewed together, using a fine needle and No. 70 thread, making a double seam as shown in Fig. 3. When all seams are completed you will have a bag the shape shown in Fig. 4. A small portion of one end or a seam must be left open for inflating. A small tube made from the cloth and sewed into one end will make a better place for inflating and to tie up tightly.

It is now necessary to varnish the bag in order to make it retain the gas. Procure 1 gal. of the very best heavy body, boiled linseed oil and immerse the bag in it. The surplus oil is squeezed out by running the bag through an ordinary clothes wringer several times. The bag is now placed in the sun for a thorough drying. Put the remaining oil in a kettle with 1/8 lb. of beeswax and boil well together. This solution is afterward diluted with turpentine so it will work well. When the bag is dry apply this mixture by rubbing it on the bag with a piece of flannel. Repeat this operation four times, being sure of a thorough drying in the sun each time. For indoor coating and drying use a small amount of plumbic oxide. This will dry rapidly in the shade and will not make the oil hard.

Fill the bag with air by using a pair of bellows and leave it over night. This test will show if the bag is airtight. If it is not tight then the bag needs another rubbing. The next operation is to fill the bag with gas.

Fig. 5—The Hydrogen Generator

Hydrogen gas is made from iron and sulphuric acid. The amounts necessary for a 10-ft. balloon are 125 lb. of iron borings and 125 lb. of sulphuric acid. 1 lb. of iron, 1 lb. of sulphuric acid and 4 lb. of water will make 4 cu. ft. of gas in one hour. Secure two empty barrels of about 52 gal. capacity and connect them, as shown in Fig. 5, with 3/4-in. pipe. In the barrel, A, place the iron borings and fill one-half full of clear water. Fill the other barrel, B, with water 2 in. above the level of the water in barrel A. This is to give a water pressure head against foaming when the generator is in action. About 15 lb. of lime should be well mixed with the water in the barrel B. All joints must be sealed with plaster of Paris. Pour in one-half of the acid into the barrel, A, with the iron borings. The barrels are kept tight while the generation is going on with the exception of the outlet, C, to the bag. When the action is stopped in the generator barrel, A, let the solution run out and fill again as before with water and acid on the iron borings. The outlet, C, should be always connected with the bag while the generator is in action. The 3/4-in. pipe extending down into the cooling tank, B, should not enter into the water over 8 in. When filled with gas the balloon is ready for a flight at the will of the operator.

It is very simple to clean a clock, which may sound rather absurd. For an amateur it is not always necessary to take the clock to pieces. With a little care and patience and using some benzine, a clean white rag, a sable brush and some oil a clock can be cleaned and put into first-class running order. The benzine should be clean and free from oil. You can test benzine by putting a little on the back of the hand; if it is good it will dry off, leaving the hand quite clean, but if any grease remains on the hand, it is not fit to use.

The oil should be of the very best that can be procured. Vegetable oils should never be used. Clock oil can be procured from your druggist or jeweler. All loose dirt should be removed from the works by blowing with bellows, or a fan, or dusting with a dry brush; in the latter case great care should be exercised not to injure any of the parts. Dip the brush in the benzine and clean the spindles and spindle holes, and the teeth of the escapement wheel. After washing a part, wipe the brush on the rag and rinse in the benzine; this should be repeated frequently, until no more dirt is seen.

When the clock has dried, oil the spindle holes carefully; this may be done with a toothpick or a sliver of woodcut to a fine point. Oil the tooth of the escapement wheel slightly, using a fine brush.

Lantern slides of a blue tone that is a pleasing variety from the usual black may be made from spoiled or old plates which have not been developed, by fixing, washing well and then dipping five minutes in the following solution:

Prepare the solutions separately and mix equal parts for use, at the time of employment. Dry the plates in the dark, and keep in the dark until used. Printing is done in the sun, and a vigorous negative must be used, says the Moving Picture World. Exposure, 20 to 30 minutes. Wash 10 minutes in running water and dry. Brown or purple tones may be had by sensitizing with the following solution instead of the above:

Bathe the plates 5 minutes, keeping the fingers out of the solution, to avoid blackened skin. Dry in the dark. Print to bronzing under a strong negative; fix in hypo, toning first if desired.

Not many amateur photographers possess a ray filter. A good substitute is to use the orange glass from the ruby lamp. This can be held in position in front of the lens with a rubber band. A longer exposure will be necessary, but good cloud effects can be procured in this manner.

Incandescent electric lamps can be made to glow so that they may be seen in a dark room by rubbing the globe on clothing or with a paper, leather or tinfoil and immediately holding near a 1/2-in. Ruhmkorff coil which is in action but not sparking. The miniature 16 cp., 20 and 22-volt lamps will show quite brilliantly, but the 110-volt globes will not glow. When experimenting with these globes everything should be dry. A cold, dry atmosphere will give best results.

Annual Regatta, Port Melbourne, Australia

For Distances up to 1000 Feet

An efficient wireless-telegraph receiving apparatus for distances up to 1,000 ft. may be constructed in the following manner: Attach a watchcase telephone receiver to a dry cell, or battery, of any make. The negative pole, or zinc, of the cell is connected to a ground wire. This is done by attaching to a gas or water pipe. The positive pole, or carbon, of the cell is connected to the aerial line. This aerial collector can be made in various ways, either by using a screen wire or numerous wires made in an open coil and hung in the air. File a V-shaped groove in the upper end of the carbon of the cell. Attach a small bent copper wire in the binding post that is attached to the zinc of the cell. In the bend of this wire and the V-shaped groove filed into the carbon, lay a needle. This will complete the receiving station. Use a spark coil in connection with a telegraph key for the sending station, making a ground with one wire, and have the other connected with another aerial line.

By connecting the telephone receiver to the cell and at the same time having a short circuit a receiving station is made. As the telephone offers a high resistance, part of the current will try to take the shorter high resistance through the needle. If the waves strike across the needle, the resistance is less, and thus less current travels through the telephone receiver. If the wave ceases, the resistance between the needle and the carbon is increased, and as less current will flow the short way, it is compelled to take the longer metallic way through the windings of the receiver, which will cause the clickings that can be heard.

Putty, when left exposed to the air, will soon become dry and useless. I have kept putty in good condition for more than a year by placing it in a glass jar and keeping it entirely covered with water.

The cell of a storage battery consists of two plates, a positive and a negative, made of lead and placed in a dilute solution of sulphuric acid. Large batteries made of large cells have a great number of plates, both positive and negative, of which all positive plates are connected to one terminal and the negative plates to the other terminal. The storage cell, as described below, is the right size to be charged by a few gravity cells and is easily made.

Secure a piece of 1-3/4-in. lead pipe, 5 in. long, and cut both ends smooth and square with the pipe. Solder a circular disk of lead to one end, forming a cup of the pipe. As this cup must hold the sulphuric acid it must be perfectly liquid-tight.

It is also necessary to get another lead pipe of the same length but only 3/4 in. in diameter. In this pipe should be bored as many 1/8 in. holes as possible, except for about 1 in. on each end. One end of this tube is hammered together as shown at A in the sketch to make a pocket to hold the paste. This, of course, does not need to be watertight.

A box of wood is made to hold the larger tube or cup. This box can be square, and the corners left open around the cup can be filled with sawdust. A support is now made from a block of wood to hold the tube, B, in place and to keep it from touching the cup C. This support or block, D, is cut circular with the same diameter as the lead cup C. The lower portion of the block is cut away so it will just fit inside of the cup to form a stopper. The center of this block is now bored to make a hole the same size as the smaller lead pipe. Place the lead pipe in the hole and immerse it in smoking hot paraffine wax, and leave it until the wood has become thoroughly saturated with the hot wax. Use care to keep the wax from running on the lead at any place other than the end within the wood block. Two binding-posts should be attached, one to the positive, or tube B, and the other to the negative, or tube C, by soldering the joint.

A paste for the positive plate is made from 1 part sulphuric acid and 1 part water with a sufficient amount of red lead added to make of thick dry consistency. When mixing the acid and water, be sure to add the acid to the water and not the water to the acid. Also remember that sulphuric acid will destroy anything that it comes in contact with and will make a painful burn if it touches the hands. Stir the mixture with a stick and when a good dry paste is formed, put it into the smaller tube and ram it down until the tube is almost filled. The paste that may have come through the holes is scraped off and the tube set aside to dry. The large tube or cup is filled with a diluted solution of sulphuric acid. This solution should be about one-twelfth acid. The cell is now complete and ready for storing the current. The cell may be charged with three gravity cells. These are connected in series and the positive terminal binding-post on the storage cell is connected to the wire leading from the copper plate in the gravity cell. The other plate is connected to the zinc. The first charge should be run into the cell for about one week and all subsequent charges should only take from 10 to 12 hours.

Fits Four Different Shaped Holes

A certain king offered to give the prince his liberty if he could whittle a plug that would fit four different shaped holes, namely: a square hole, a round one, an oblong one and a triangular one, says the Pathfinder. A broomstick was used to make the plug and it was whittled in the shape shown in Fig. 1. The holes in the different places as shown in Fig. 2, were fitted by this one plug.

Secure a piece of wood about 3-1/2 in. square that will furnish a nice finish and round the corners and make a small rounding edge as shown in the sketch. From a piece of brass 1/16 in. thick cut two pieces alike, A and B, and match them together, leaving about 1/16 in. between their upper edges and fasten them to the wood with binding-posts. The third piece of brass, C, is fitted between the pieces A and B allowing a space of 1/16-in. all around the edge. One binding-post and a small screw will hold the piece of brass, C, in place on the wood. The connections are made from the line wires to the two upper binding-posts and parallel from the lower binding-posts to the instrument. The third binding-post on C is connected to the ground wire. Any heavy charge from lightning will jump the saw teeth part of the brass and is grounded without doing harm to the instruments used.

Contributed by Edwin Walker, Chicago, Ill.

Easy to Build and Safe to Use

A flat bottom boat is easy to make and is one of the safest boats, as it is not readily overturned. It has the advantage of being rowed from either end, and has plenty of good seating capacity.

This punt, as shown in Fig. 1, is built 15 ft. long, about 20 in. deep and 4 ft. wide. The ends are cut sloping for about 20 in. back and under. The sides are each made up from boards held together with battens on the inside of the boat near the ends and in the middle. One wide board should be used for the bottom piece. Two pins are driven in the top board of each side to serve as oarlocks.

The bottom is covered with matched boards not over 5 in. wide. These pieces are placed together as closely as possible, using white lead between the joints and nailing them to the edges of the side boards and to a keel strip that runs the length of the punt, as shown in Fig. 2. Before nailing the boards place lamp wicking between them and the edges of the side boards. Only galvanized nails should be used. In order to make the punt perfectly watertight it is best to use the driest lumber obtainable. At one end of the punt a skag and a rudder can be attached as shown in Fig. 3.

Adjustable to Any Height

When using developing papers it is always bothersome to build up books or small boxes to make a place to set the printing frame in front of the light. Details for making a small stand that is adjustable to any desired height are shown in the sketch. In Fig. 1 is shown the construction of the sliding holder. A piece of 1/4-in. gas pipe, A, is cut 1 in. long and fitted with a thumbscrew, B. The piece of pipe is soldered to the middle on the back side of a piece of metal that is about 4 by 4-1/2 in. with its lower edge turned up to form a small shelf as shown at C. The main part of the stand is made by inserting a 5/16-in. rod tightly into a block of hard maple wood that is 1 in. thick and 3-1/2 in. square (Fig 2). The pipe that is soldered to the metal support will slide up and down the rod and the thumbscrew can be set to hold it at the desired point.

Take an electric light bulb from which the air has not been exhausted and immerse it in water and then break off the point. As there is a vacuum in the bulb it will quickly fill with water. Shake the bulb gently until a part of the water is out and then screw the bulb into a socket with the point always downward. Apply the current and the heated air inside will soon expand and force the water out with great rapidity. Sometimes this experiment can be done several times by using the same bulb.

Contributed by Curtiss Hill, Tacoma, Wash.

The accompanying illustration is a remarkable photograph of a streak of lightning. Many interesting pictures of this kind can be made during a storm at night. The camera is set in a place where it will not get wet and left standing with the shutter open and the plate ready for the exposure. Should a lightning streak appear within the range of the lens it will be made on the plate, which can be developed in the usual manner. It will require some attention to that part of the sky within the range of the lens so as to not make a double exposure by letting a second flash enter the open lens.

Contributed by Charles H. Wagner.

The following notes on a small single-phase induction motor, without auxiliary phase, which the writer has made, may be of interest to some of our readers, says the Model Engineer. The problem to be solved was the construction of a motor large enough to drive a sewing machine or very light lathe, to be supplied with 110-volt alternating current from a lighting circuit, and to consume, if possible, no more current than a 16-cp. lamp. In designing, it had to be borne in mind that, with the exception of insulated wire, no special materials could be obtained.

The principle of an induction motor is quite different from that of the commutator motor. The winding of the armature, or "rotor," has no connection with the outside circuit, but the current is induced in it by the action of the alternating current supplied to the winding of the field-magnet, or "stator." Neither commutator nor slip rings are required, and all sparking is avoided. Unfortunately, this little machine is not self-starting, but a slight pull on the belt just as the current is turned on is all that is needed, and the motor rapidly gathers speed provided no load is put on until it is in step with the alternations of the supply. It then runs at constant speed whether given much or little current, but stops if overloaded for more than a few seconds.

The stator has four poles and is built up of pieces of sheet iron used for stove pipes, which runs about 35 sheets to the inch. All the pieces are alike and cut on the lines with the dimensions as shown in Fig. 1, with the dotted line, C, to be filed out after they are placed together. Each layer of four is placed with the pointed ends of the pieces alternately to the right and left so as to break joints as shown in Fig. 2. The laminations were carefully built up on a board into which heavy wires had been driven to keep them in place until all were in position and the whole could be clamped down. In the middle of the pieces 1/4-in. holes, B, were then drilled and 1/4-in. bolts put in and tightened up, large holes being cut through the wood to enable this to be done. The armature tunnel was then carefully filed out and all taken apart again so that the rough edges could be scraped off and the laminations given a thin coat of shellac varnish on one side. After assembling a second time, the bolts were coated with shellac and put into place for good. Holes 5-32 in. in diameter were drilled in the corners, A, and filled with rivets, also varnished before they were put in. When put together they should make a piece 2 in. thick.

This peculiar construction was adopted because proper stampings were not available, and as every bit of sheet iron had to be cut with a small pair of tinners' snips, it was important to have a very simple outline for the pieces. They are not particularly accurate as it is, and when some of them got out of their proper order while being varnished, an awkward job occurred in the magnet which was never entirely corrected. No doubt some energy is lost through the large number of joints, all representing breaks in the magnetic circuit, but as the laminations are tightly held together and the circuit is about as compact as it could possibly be, probably the loss is not as great as it would appear at first sight.

The rotor is made of laminations cut from sheet iron, as shown in Fig. 3, which were varnished lightly on one side and clamped on the shaft between two nuts in the usual way. A very slight cut was taken in the lathe afterwards to true the circumference. The shaft was turned from 1/2-in. wrought iron, no steel being obtainable, and is shown with dimensions in Fig. 4. The bearings were cast of babbitt metal, as shown in Fig. 5, in a wooden mold and bored to size with a twist drill in the lathe. They are fitted with ordinary wick lubricators. Figures 6 and 7 are sections showing the general arrangement of the machine.

The stator is wound full with No. 22 double cotton-covered copper wire, about 2-1/2 lb. being used, and the connections are such as to produce alternate poles—that is, the end of the first coil is joined to the end of the second the beginning of the second to the beginning of the third, and the end of the third to the end of the fourth, while the beginnings of the first and fourth coils connect to the supply.

The rotor is wound with No. 24 double cotton-covered copper wire, each limb being filled with about 200 turns, and all wound in the same direction. The four commencing ends are connected together on one side of the rotor and the four finishing ends are soldered together on the other. All winding spaces are carefully covered with two layers of cambric soaked in shellac, and as each layer of wire was wound, it was well saturated with varnish before the next was put on.

This type of motor has drawbacks, as before stated, but if regular stampings are used for the laminations, it would be very simple to build, having no commutator or brushes, and would not easily get out of order. No starting resistance is needed, and as the motor runs at constant speed, depending upon the number of alterations of the supply, a regulating resistance is not needed.

The pain of carbolic acid burns can be relieved promptly by washing with alcohol, if applied immediately. If too late for alcohol to be of use, brush with water containing saturated solution of picric acid.

To Protect Book Covers

Book covers become soiled in handling and especially school books. Various methods are applied for making a temporary cover that will protect the book cover. A paper cover can be quickly made by using a piece of paper larger than both covers on the book when they are open. Fold the paper on the long dotted line, as shown in Fig. 1. When the folds are made the paper should then be just as wide as the book cover is high. The ends are then folded on the short dotted lines, which will make it appear as shown in Fig. 2. The paper thus folded is placed on the book cover as shown in Fig. 3.

Contributed by C. E. McKinney, Jr., Newark, N. J.

The Camera as It is Arranged in Front of the Window for Reducing the Size of a Picture, and the Method of Binding the Slides

The popularity of lantern slides, and especially of colored ones, as a means of illustrating songs, has caused so large a demand for this class of work that almost any amateur may take up slide making at a good profit. The lantern slide is a glass plate, coated with slow and extremely fine-grained emulsion. The size is 3-1/4 by 4 in. A lantern slide is merely a print on a glass plate instead of on paper. Lantern slides can be made in two different ways. One is by contact, exactly the same as a print is made on paper, and the other by reduction in the camera. In making slides by contact, select the negative and place it in the printing frame and put the lantern plate upon it, film to film. Clamp down the back and expose just as in making a print. A good method of exposing is to hold a lighted match about 3 in. from the frame for three or more seconds according to the density.

Development is carried on in the same manner as with a negative. The image should appear in. about a minute, and development should be over in three or four minutes. If the exposure has been correct, the high lights will stay white throughout the development and will come out as clear glass after fixing. It is best to use the developers recommended by the manufacturer of the plates used, the formulas being found in each package of plates. It is best, also, to use a plain fixing bath, which must be fresh and kept as cool as possible in hot weather.

The lantern-slide film that is new on the market can be handled in the same manner as the glass-plate slide, except that the binding is different. The results are the same and the slides are not so bulky to handle. Being unbreakable, they are much used by travelers. The manner of binding them for use in a lantern is described on the circular enclosed with the film.

When the negative is larger than the lantern-slide plate, and it is desirable to reduce the entire view upon the slide, a little extra work will be necessary. Select a room with one window, if possible, and fit a light-proof frame into it to keep out all light with the exception of a hole in which to place the negative, as shown in Fig. 1. Unless this hole is on a line with the sky it will be necessary to place a sheet of white cardboard at an angle of 45 deg. on the outside of the frame to reflect the light through the negative as shown in Fig. 2. Make or secure an inside kit to place in the plate holder of your camera to hold the lantern slide plate as shown in Fig. 3. Draw lines with a pencil, outlining on the ground glass of the camera the size of the lantern slide plate, and in the place where the plate will be in the plate holder when placed in position in the camera. This will enable you to focus to the proper size. Place the camera in front of the hole in the frame, place the negative in the hole and focus the camera for the lantern slide size. Expose with a medium stop for about 20 seconds and treat the plate the same as with the contact exposure.

When dry the lantern slide plate may be tinted any color by means of liquid colors. These can be purchased from any photo material store. In coloring the slide plate it is only necessary to moisten the gelatine film from time to time with a piece of cloth dampened in water. The colors may then be spread evenly with a soft brush, which should be kept in motion to prevent spots. The slide is put together by placing a mat made of black paper, as shown in Fig. 4, on the gelatine side of the lantern slide, A, Fig. 5, and then a plain glass, B, over the mat, C, and the three bound together with passe-partout tape, D. Contrasty negatives make the best slides, but the lantern slide plate should be made without any attempt to gain density.

The material needed for making this porch swing chair are two pieces of round wood 2-1/2 in. in diameter and 20 in. long, and two pieces 1-1/4 in. in diameter and 40 in. long. These longer pieces can be made square, but for appearance it is best to have them round or square with the corners rounded. A piece of canvas, or other stout cloth, 16 in. wide and 50 in. long, is to be used for the seat. The two short pieces of wood are used for the ends of the chair and two 1-in. holes are bored in each end of them 1-1/2 in. from the ends, and between the holes and the ends grooves are cut around them to make a place to fasten ropes, as shown at B, Fig. 1. The two longer pieces are used for the sides and a tenon is cut on each end of them to fit in the 1-in. holes bored in the end pieces, as shown at A, Fig. 1. The canvas is now tacked on the end pieces and the pieces given one turn before placing the mortising together.

The chair is now hung up to the porch ceiling with ropes attached to a large screw eye or hook. The end of the chair to be used for the lower part is held about 16 in. from the floor with ropes direct from the grooves in the end pieces to the hook. The upper end is supported by using a rope in the form of a loop or bail, as shown in Fig. 2. The middle of the loop or bail should be about 15 in. from the end piece of the chair. Another rope is attached to the loop and through the hook and to a slide as shown. This will allow for adjustment to make the device into a chair or a hammock.

Contributed by Earl R. Hastings, Corinth, Vt.

Make a small black circular dot 1/2 in. in diameter on a piece of cardboard and about 3 in. from the center of this dot draw a star. Hold the cardboard so that the star will be directly in front of one eye, while the dot will be in front of the other. If the star is in front of the left eye, close the right eye and look steadily at the star while you move the cardboard until the point is reached where the dot disappears. This will prove the presence of a blind spot in a person's eye. The other eye can be given the same experiment by turning the cardboard end for end. The blind spot does not indicate diseased eyes, but it simply marks the point where the optic nerve enters the eyeball, which point is not provided with the necessary visual end organs of the sight, known as rods and cones.

A wax from the rafie palm of Madagascar is being used as a substitute for beeswax.

The accompanying sketch illustrates a very ingenious device which does the family washing, as well as to operate other household machines. A disk 1 in. in thickness and 10 in. in diameter was cut from a piece of rough board, and on its circumference were nailed a number of cup-shaped pieces cut from old tin cans. A hole was then bored through the center of the disk and an old piece of iron rod was driven through to form a shaft. Two holes were then bored opposite each other through the sides of a wooden box in which the disk was placed, allowing the shaft to project through the holes. A small grooved wooden pulley was driven tightly on one of the projecting ends of the shaft. The top of the box was then tightly closed and a hole, large enough to admit the nozzle of a garden hose, was bored so that the jet of water would flow upon the tin buckets that were nailed to the circumference of the wheel or disk. Another hole was bored in the bottom of the box large enough to allow the waste water to run away freely. A belt, made from an ordinary sash cord, was run from the small pulley on the waterwheel to a large pulley, as shown in Fig. 1. A pitman was attached to the large pulley, which operates the washing machine by its reciprocating motion, and the length of the stroke is adjusted by moving the position of the hinge joint on the arm of the washing machine, as shown in Fig. 2. The pressure at the nozzle is about 20 lb. per square inch, and is sufficient to drive the waterwheel under all ordinary circumstances.

Contributed by P. J. O'Gara, Auburn, Cal,

When looking at the accompanying sketch you will say that the letters are alternately inclined to the right and left. They are not so and can be proved by measuring the distance of the top and bottom of any vertical strokes from the edge of the entire block. They will be found to be exactly the same distance. Or take any of the horizontal strokes of the four letters and see how far their extremities are from the top and bottom of the entire block. It will be found that a line joining the extremities of the strokes are strictly parallel to the top or bottom and that they are not on a slant at all. It is the slant of the numerous short lines that go to make up the letter as a whole that deceives the eye.

It often becomes necessary to find the thickness of material so thin, or inconvenient to measure, that a rule or other measuring device will not serve the purpose. A simple, fairly accurate, and easily made apparatus of the micrometer form may be constructed as shown by the accompanying sketch. Secure a common iron or brass bolt about 1/4-in. in diameter and about 2-1/2 in. long, with as fine a thread as possible, and the thread cut to within a short distance of the head of the bolt. The head of the bolts should have a slot cut for the use of a screwdriver. Clamp together two blocks of wood with square corners which are about 1 in. wide, 3/4 in. thick and 2-1/2 in. long and fasten them together with small pieces nailed across the ends. The width of the blocks will then be about 2 in. Bore a 1/4-in. hole through the center of the blocks in the 2 in. direction. Remove the clamp and set the nut into one of the blocks, so that the hole will be continuous with the hole in the wood. Cut out a piece from the block combination, leaving it shaped like a bench, and glue the bottoms of the legs to a piece of thin board about 2-1/2 in. square for a support.

Solder one end of a stiff wire that is about 2 in. long to the head of the bolt at right angles to the shaft, and fix a disc of heavy pasteboard with a radius equal to the length of the wire, and with its circumference graduated into equal spaces, to serve in measuring revolutions of the end of the wire, to the top of the bench. Put the bolt in the hole, screwing it through the nut, and the construction is complete. The base is improved for the measuring work by fastening a small piece of wood on the board between the legs of the bench. A small piece of metal is glued on this piece of wood at the point where the bolt meets it.

Find the number of threads of the screw to the inch by placing the bolt on a measuring rule, and counting the threads in an inch of its length. The bolt in making one revolution will descend a distance equal to the distance between the threads.

The device is used by placing the object whose thickness is to be measured on the base under the bolt, and screwing the bolt down until its end just touches the object, then removing the object, and screwing the bolt down until its end just touches the base, carefully noting while doing so the distance that the end of the wire moves over the scale. The part of a rotation of the bolt, or the number of rotations with any additional parts of a rotation added, divided by the number of threads to the inch, will be the thickness of the object. Quite accurate measurements may be made with this instrument, says the Scientific American, and in the absence of the expensive micrometer, it serves a very useful purpose.

Break a portion of the end off from a 16-cp. globe that has been thrown away as useless. Shake the globe until all the filament is broken away, leaving only the ends of the platinum wire exposed. Screw the globe into a socket that sets upright and fill it with salt water. Make one connection to the socket from the positive wire of a 110 volt circuit and the other to a ground. When the current is turned on small stars will be seen in the globe, which show up fine at night.

Contributed by Lindsay McMillan, Santa Maria, Oal.

Two or three applications of milk which are wiped up with a dry cloth will remove india ink spots on carpets.

Among the numerous physical exercises is the feat of balancing on the two rear legs of a chair while one foot rests on the front part of the seat and the other on the back of the chair. This may appear to be a hard thing to do, yet with a little practice it may be accomplished. This exercise is one of many practiced by the boys of a boys' home for an annual display given by them. A dozen of the boys will mount chairs at the same time and keep them in balance at the word of a commanding officer.

Side and Top View

A 6 by 6-in. piece of wood 12 ft. long is used for the center pole. Bore a 3/4-in. hole in each end to a depth of 6 in. Place a 3/4-in. bolt in each hole, the bolt being long enough to protrude 2 in. beyond the end of the wood. Short pieces of wood are nailed on the center pole about 2 ft. from the end that is to be used for the bottom. This should form a hub on which to place the inner ends of the extending spokes that hold the platform. The spokes are made from twelve pieces of 2 by 4-in. material 12 ft. long.

Usually a wheel can be found in a scrap pile suitable to place on the pin that is in the top end of the center pole. The wheel should be open or have spokes. This wheel is used to attach wires for guying. The bottom pin in the center pole is placed in a hole that is bored into a block of wood about 12-in. square and 3 or 4 in. thick. A piece of sheet metal should be drilled and placed on the pin between the block and end of the pole to make a smooth bearing. The center pole is now placed in position and guyed with six wires that are about 35 ft. long. Stakes are driven into the ground and the wires fastened to them and to the wheel at the top end of the pole. Care should be taken when attaching the wires to get the center pole to stand perpendicular. Twelve hooks should be placed at equal distances around the center pole about 1 ft. from the top end. Wires are fastened to these hooks and to the twelve 2 by 4-in. pieces used for the spokes. The wires should be tied around each spoke about 2 ft. from the ends. Space the spokes with equal divisions and cover the outer 2 ft. of the ends with boards, as shown in the plan sketch on the right hand end of the drawing. The boards may be nailed or bolted. If bolted and the wires made in a loop at the hooks, the swing can easily be taken apart and changed from one place to another.

Contributed by A. O. Graham, Fort Worth, Tex.

The frame of the lamp is made from bar metal 3/4 in. wide and 1/8 in. thick, bent and welded to make a continuous loop in the shape as shown at G in the sketch. This frame should be about 10-1/2 in. long with the upper or wider part 4 in. long, and the lower part 6-1/2 in. long. The width should be about 5-1/4 in. at the top and 4 in. at the bottom. A cross bar, L, made of the same material, is fitted into the off-set in the frame and riveted. Holes are drilled through the frame and brass bushings, H and J, are fitted for bearings to receive the adjusting brass rod, B, which should be 1/4 in. in diameter. A brass curtain rod can be used for the rod B, and on its lower end a socket, P, is soldered.

A piece of brass 2 in. long, 1/2 in. wide and 1/8 in. thick is used for the armature, A, to be operated by the magnet coil, C. The coil, C, is made in the usual manner by wrapping No. 14 cotton-covered magnet wire on a wooden spool that has a soft iron core. The spool is about 2-1/2 in. long. The armature, A, is drilled, making a hole just a little larger than the rod, B, and is adjusted in place by two set screws, D and E. A soft piece of iron, F, is fastened to the opposite end of the armature with a screw, which should be placed directly under the end of the coil's core. This end of the armature may be kept from swinging around by placing it between a U-shaped piece of brass fastened to the cross piece L. At the bottom end of the frame, and directly centering the holes H and J, a hole is drilled to receive a hard rubber bushing, R, for insulating the brass ferrule, S, that holds the lower carbon.

One connection is made from the main to the upper binding-post, which is in turn connected to one terminal of the coil, C, the other coil terminal being attached to the frame. The other main connection is made to the lower binding-post, which is also connected to the brass ferrule, S, by soldering. The two binding-posts are insulated from the frame the same as the ferrule S. When using on a 110-volt circuit there must be some resistance in connection, which may be had by using German silver wire, or a water rheostat heretofore described.

Contributed by Arthur D. Bradley. Randolph, Mass.

The Mexican government has appropriated $25,000,000 for irrigation work.

Take a smooth hexagon lead pencil, one without either rubber or metal end, and place it against a door or window casing; then with a firm, heavy pressure slide the pencil some 3 or 4 in. and it will stay as if glued to the casing. You may now hang your hat on the end of the pencil.

When you slide the pencil along the casing, do it without any apparent effort, and it will appear to your audience as though you had hypnotized it. This is a very neat trick if performed right. Figure 1 shows the pencil on the casing and Fig. 2 the hat hanging on it.

A Secure Knot

One of the most prominent English football clubs kept the tying of this knot on the rubber hose of their football a secret and never allowed all of its members to know how it was tied. This tie can be used on grain sacks, and in numerous other like instances. Make one loop in the cord and then another exactly the same way, as shown in Fig. 1, placing the end of the cord under the first loop, then pulling at each end of the cord as in Fig. 2.

A.E.J.

Stove polish consists of 2 parts graphite, 4 parts copperas and 2 parts bone black, mixed with water to form a paste.

Details of Induction Coil

There is nothing quite so startling as to receive an electric shock unexpectedly and such a shock may be given to a friend while shaking hands upon meeting. The shock produced is not harmful and the apparatus can be carried in the pocket. It consists of a small induction coil that can be constructed at home.

The core of the coil, A, Fig. 1, is constructed in the usual manner, of small soft-iron wire to make a bundle about 3/16 in. in diameter and 2 in. long. The coil ends are made from cardboard, about 1 in. in diameter, with a 3/16-in. hole in the center. The hole should be cut as shown in Fig. 2, so as to have four small pieces that can be bent out, leaving the projections as shown. After wrapping three or four turns of paper around the bundle of wires the cardboard ends are put on with the projections inside, so the coils of wire will hold them in place. About 70 turns of No. 24 gauge double covered magnet wire is first placed on the core, for the primary, and then 1,500 turns of No. 32 or 34 gauge double-covered wire is wrapped on top of the primary, for the secondary. Sufficient length of wire must be left outside at each end of both windings to make connections. The vibrator B, Fig. 1, and the support C are made from thin spring steel, about 1/8 in. wide, bent as shown and securely fastened to the cardboard end of the coil. The armature is made from a soft piece of iron, about 3/16 in. in diameter and 1/16 in. thick, which is soldered to the end of the vibrator directly opposite the end of the core. A small screw is fitted in the end of the support, C, for adjustment, which should be tipped with platinum and also a small piece of platinum placed where the screw will touch the vibrator, B.

One of the primary wires is connected to the screw support. The vibrator, is connected to a flash lamp battery, D. The other primary wire is connected to a switch, S, which in turn is connected to the other terminal of the battery. The switch, S, may be made from a 3/8-in. cork with the wires put through about 3/16 in. apart and allow them to project about 1/2 in. The plate E is cut about 1/2 in. square from a piece of copper and is fastened to the heel of one shoe and connected with a wire from the secondary coil which must be concealed inside of the trouser leg. The other secondary wire is connected through the coat sleeve to a finger ring, F. The vibrator screw must be properly adjusted. When the vibrator is not working the armature should be about 1/16 in. from the core and directly opposite.

The coil when complete will be about 2-1/2 in. long and 1 in. in diameter. The coil can be placed in an old box that has been used for talcum powder or shaving stick. The space around the coil in the box can be filled with paper to keep it tight.

The coil and battery are carried in the pockets and the cork button put in the outside coat pocket, where it can be pressed without attracting attention.

Place a small piece of paper, lighted, in an ordinary water glass. While the paper is burning turn the glass over and set into a saucer previously filled with water. The water will rapidly rise in the glass, as shown in the sketch.

A small combination lock for chests can be purchased for a small sum of money and attached to a trunk cover after first removing the old lock as shown in Fig. 1. It is necessary to add 1/2-in. to the thickness of the trunk lid or cover. This may be done by placing a brass plate 1/8-in. thick on the outside and a board 3/8-in. thick on the inside. The lock, brass plate, board and trunk cover are all securely riveted together. The support for the dial is soldered to the brass plate.

The hasp, if that be the name for the double toothed arrangement that catches into the lock, was to be secured by only three brass screws, which seemed to be insufficient, says a correspondent of the Metal Worker; therefore a piece of heavy tin was formed over the front of the trunk, which is only 3/8-in. board, the hasp tinned and soldered to the back of the now U-shaped tin, and the tin placed over the board and all fastened in position. The tin is 4 in. wide, 16 in. long and when placed over the board, it laps down about 8 in. between the boards, and the same distance inside of the new board, as shown by the heavy line in the cross section, Fig. 1. Wrought nails are used which pass twice through the tin and both boards, and then well clinched. The three screws were then put in the hasp.

The knob on the dial extends out too far, which may be filed off and two holes substituted, as shown, with which to operate the dial. An old key is filed down in the shape shown in Fig. 2 to fit the two holes. As the dial is convex it will need protection to prevent injury by rough handling. A leather shield may be used for this purpose, which is cut with two holes, one for the key and the other to permit the operator to observe the numbers on the dial. The shield answers a further purpose of preventing any bystander from noting the numbers on the dial.

Construction of Magic Boxes

Four Electric Magic Boxes Complete for Use