Articles in This Slice

248

CAPEFIGUE, JEAN-BAPTISTE HONORÉ RAYMOND (1801-1872), French historian and biographer, was born at Marseilles in 1801. At the age of twenty he went to Paris to study law; but he soon deserted law for journalism. He became editor of the Quotidienne, and was afterwards connected, either as editor or leading contributor, with the Temps, the Messager des Chambres, the Révolution de 1848 and other papers. During the ascendancy of the Bourbons he held a post in the foreign office, to which is due the royalism of some of his newspaper articles. Indeed all Capefigue’s works receive their colour from his legitimist politics; he preaches divine right and non-resistance, and finds polite words even for the profligacy of Louis XV. and the worthlessness of his mistresses. He wrote biographies of Catherine and Marie de’ Medici, Anne and Maria Theresa of Austria, Catherine II. of Russia, Elizabeth of England, Diana of Poitiers and Agnes Sorel—for he delighted in passing from “queens of the right hand” to “queens of the left.” His historical works, besides histories of the Jews from the fall of the Maccabees to the author’s time, of the first four centuries of the Christian church, and of European diplomatists, extend over the whole range of French history. He died at Paris in December 1872.

CAPEL (of Hadham), ARTHUR CAPEL, Baron (fl. 1640-1649), English royalist, son of Sir Henry Capel of Rayne Hall, 249 Essex, and of Theodosia, daughter of Sir Edward Montagu of Broughton, Northamptonshire, was elected a member of the Short and Long Parliaments in 1640 for Hertfordshire. He at first supported the opposition to Charles’s arbitrary government, but soon allied himself with the king’s cause, on which side his sympathies were engaged, and was raised to the peerage by the title of Baron Capel of Hadham on the 6th of August 1641. On the outbreak of the war he was appointed lieutenant-general of Shropshire, Cheshire and North Wales, where he rendered useful military services, and later was made one of the prince of Wales’s councillors, and a commissioner at the negotiations at Uxbridge in 1645. He attended the queen in her flight to France in 1646, but disapproved of the prince’s journey thither, and retired to Jersey, subsequently aiding in the king’s escape to the Isle of Wight. He was one of the chief leaders in the second Civil War, but met with no success, and on the 27th of August, together with Lord Norwich, he surrendered to Fairfax at Colchester on promise of quarter for life.1 This assurance, however, was afterwards interpreted as not binding the civil authorities, and his fate for some time hung in the balance. He succeeded in escaping from the Tower, but was again captured, was condemned to death by the new “high court of justice” on the 8th of March 1649, and was beheaded together with the duke of Hamilton and Lord Holland the next day. He married Elizabeth, daughter and heir of Sir Charles Morrison of Cassiobury, Hertfordshire, through whom that estate passed into his family, and by whom besides four daughters he had five sons, the eldest Arthur being created earl of Essex at the Restoration. Lord Capel, who was much beloved, and who was a man of deep religious feeling and exemplary life, wrote Daily Observations or Meditations: Divine, Morall, published with some of his letters in 1654, and reprinted, with a short life of the author, under the title Excellent Contemplations, in 1683.

CAPEL CURIG, a tourist resort in Carnarvonshire, North Wales, 14½ m. from Bangor. It is a collection of a few houses, too scattered to form a village properly so called. At the Roberts hotel is shown on a window pane the supposed signature of Wellington. The road from Bettws y coed, past the Swallow Falls to Capel Curig, and thence to Llanberis and Carnarvon, is very interesting, grand and lonely. Excellent fishing is to be had here, chiefly for trout. In summer, coaching tours discharge numbers of visitors daily; the railway station is Bettws (London & North-Western railway). Capel Curig means “chapel of Curig,” a British saint mentioned in Welsh poetry. The place is a centre for artists, geologists and botanists, for the ascent of Snowdon, Moel Siabod, Glydyr Fawr, Glydyr Fach, Tryfan, &c., and for visiting Llyn Ogwen, Llyn Idwal, Twll du (Devil’s Kitchen), Nant Ffrancon and the Penrhyn quarries.

CAPELL, EDWARD (1713-1781), English Shakespearian critic, was born at Troston Hall in Suffolk on the 11th of June 1713. Through the influence of the duke of Grafton he was appointed to the office of deputy-inspector of plays in 1737, with a salary of £200 per annum, and in 1745 he was made groom of the privy chamber through the same influence. In 1760 appeared his Prolusions, or Select Pieces of Ancient Poetry, a collection which included Edward III., placed by Capell among the doubtful plays of Shakespeare. Shocked at the inaccuracies which had crept into Sir Thomas Hanmer’s edition of Shakespeare, he projected an entirely new edition, to be carefully collated with the original copies. After spending three years in collecting, and comparing scarce folio and quarto editions, he published his own edition in 10 vols. 8vo (1768), with an introduction written in a style of extraordinary quaintness, which was afterwards appended to Johnson’s and Steevens’s editions. Capell published the first part of his commentary, which included notes on nine plays with a glossary, in 1774. This he afterwards recalled, and the publication of the complete work, Notes and Various Readings of Shakespeare (1779-1783), the third volume of which bears the title of The School of Shakespeare, was completed, under the superintendence of John Collins, in 1783, two years after the author’s death. It contains the results of his unremitting labour for thirty years, and throws considerable light on the history of the times of Shakespeare, as well as on the sources from which he derived his plots. Collins asserted that Steevens had stolen Capell’s notes for his own edition, the story being that the printers had been bribed to show Steevens the sheets of Capell’s edition while it was passing through the press. Besides the works already specified, he published an edition of Antony and Cleopatra, adapted for the stage with the help of David Garrick in 1758. His edition of Shakespeare passed through many editions (1768, 1771, 1793, 1799, 1803, 1813). Capell died in the Temple on the 24th of February 1781.

CAPELLA, MARTIANUS MINNEUS FELIX, Latin writer, according to Cassiodorus a native of Madaura in Africa, flourished during the 5th century, certainly before the year 439. He appears to have practised as a lawyer at Carthage and to have been in easy circumstances. His curious encyclopaedic work, entitled Satyricon, or De Nuptiis Philologiae et Mercurii et de septem Artibus liberalibus libri novem, is an elaborate allegory in nine books, written in a mixture of prose and verse, after the manner of the Menippean satires of Varro. The style is heavy and involved, loaded with metaphor and bizarre expressions, and verbose to excess. The first two books contain the allegory proper—the marriage of Mercury to a nymph named Philologia. The remaining seven books contain expositions of the seven liberal arts, which then comprehended all human knowledge. Book iii. treats of grammar, iv. of dialectics, v. of rhetoric, vi. of geometry, vii. of arithmetic, viii. of astronomy, ix. of music. These abstract discussions are linked on to the original allegory by the device of personifying each science as a courtier of Mercury and Philologia. The work was a complete encyclopaedia of the liberal culture of the time, and was in high repute during the middle ages. The author’s chief sources were Varro, Pliny, Solinus, Aquila Romanus, and Aristides Quintilianus. His prose resembles that of Apuleius (also a native of Madaura), but is even more difficult. The verse portions, which are on the whole correct and classically constructed, are in imitation of Varro and are less tiresome.

A passage in book viii. contains a very clear statement of the heliocentric system of astronomy. It has been supposed that Copernicus, who quotes Capella, may have received from this work some hints towards his own new system.

CAPE MAY, a city and watering-place of Cape May county, New Jersey, U.S.A., on the Atlantic coast, 2 m. E.N.E. of Cape May, the S. extremity of the state, and about 80 m. S. by E. of Philadelphia. Pop. (1890) 2136; (1900) 2257; (1905) 3006; (1910) 2471. Cape May is served by the Maryland, Delaware & Virginia (by ferry to Lewes, Delaware), the West Jersey & Seashore (Pennsylvania system), and the Atlantic City (Reading system) railways, and, during the summer season, by steamboat to Philadelphia. The principal part of the city is on a peninsula (formerly Cape Island) between the ocean and Cold Spring inlet, which has been dredged and is protected by jetties to make a suitable harbour. The further improvement of the inlet and the harbour was authorized by Congress in 1907. On the ocean side, along a hard sand beach 5 m. long, is the Esplanade. There are numerous hotels and handsome cottages for summer visitors, who come especially from Philadelphia, from New York, from the South and from the West. Cape May offers good bathing, yachting and fishing, with driving and hunting in the wooded country inland from the coast. At Cape May Point is the Cape May lighthouse, 145 ft. high, built in 1800 and rebuilt in 1859. In the city are canneries of vegetables and fruit, glass-works and a gold-beating establishment. Fish and oysters are exported. Cape May was named by Cornelis Jacobsen Mey, director of the Prince Hendrick (Delaware) river for the West India Company of 250 Holland, who took possession of the river in 1623, and planted the short-lived colony of Fort Nassau 4 m. below Philadelphia, near the present Gloucester City, N.J. Cape May was settled about 1699,—a previous attempt to settle here made by Samuel Blommaert in 1631 was unsuccessful. It was an important whaling port early in the 18th century, and became prominent as a watering-place late in that century. It was incorporated as the borough of Cape Island in 1848, and chartered as the city of Cape Island in 1851; in 1869 the name was changed to Cape May.

CAPENA, an ancient city of southern Etruria, frequently mentioned with Veii and Falerii. Its exact site is, however, uncertain. According to Cato it was a colony of the former, and in the wars between Veii and Rome it appears as dependent upon Veii, after the fall of which town, however, it became subject to Rome. Out of its territory the tribus Stellatina was formed in 367 b.c. In later republican times the city itself is hardly mentioned, but under the empire a municipium Capenatium foederatum is frequently mentioned in inscriptions. Of these several were found upon the hill known as Civitucola, about 4 m. north-east of the post station of ad Vicesimum on the ancient Via Flaminia, a site which is well adapted for an ancient city. It lies on the north side of a dried-up lake, once no doubt a volcanic crater. Remains of buildings of the Roman period also exist there, while, in the sides of the hill of S. Martino which lies on the north-east,1 rock-cut tombs belonging to the 7th and 6th centuries b.c. but used in Roman times for fresh burials, were excavated in 1859-1864, and again in 1904. Inscriptions in early Latin and in local dialect were also found (W. Henzen, Bullettino dell’ Istituto, 1864, 143; R. Paribeni, Notizie degli Scavi, 1905, 301). Similar tombs have also been found on the hills south of Civitucola. G.B. de Rossi, however, supposed that the games of which records (fragments of the fasti ludorum) were also discovered at Civitucola, were those which were celebrated from time immemorial at the Lucus Feroniae, with which he therefore proposed to identify this site, placing Capena itself at S. Oreste, on the south-eastern side of Mount Soracte. But there are difficulties in the way of this assumption, and it is more probable that the Lucus Feroniae is to be sought at or near Nazzano, where, in the excavation of a circular building which some conjecture to have been the actual temple of Feronia, inscriptions relating to a municipality were found. Others, however, propose to place Lucus Feroniae at the church of S. Abbondio, 1 m. east of Rignano and 4 m. north-north-west of Civitucola, which is built out of ancient materials. On the Via Flaminia, 26 m. from Rome, near Rignano, is the Christian cemetery of Theodora.

CAPER, FLAVIUS, Latin grammarian, flourished during the and century. He devoted special attention to the early Latin writers, and is highly spoken of by Priscian. Caper was the author of two works—De Lingua Latina and De Dubiis Generibus. These works in their original form are lost; but two short treatises entitled De Orthographia and De Verbis Dubiis have come down to us under his name, probably excerpts from the original works, with later additions by an unknown writer.

CAPERCALLY, or Caperkally,1 a bird’s name commonly derived from the Gaelic capull, a horse (or, more properly, a mare), and coille, a wood, but with greater likelihood, according to the opinion of Dr M‘Lauchlan, from cabher, an old man (and, by metaphor, an old bird), and coille, the name of Tetrao urogallus, the largest of the grouse family (Tetraonidae), and a species which was formerly indigenous to Scotland and Ireland. The word is frequently spelt otherwise, as capercalze, capercailzie (the z, a letter unknown in Gaelic, being pronounced like y), and capercaillie, and the English name of wood-grouse or cock-of-the-wood has been often applied to the same bird. The earliest notice of it as an inhabitant of North Britain seems to be by Hector Boethius, whose works were published in 1526, and it can then be traced through various Scottish writers, to whom, however, it was evidently but little known, for about 200 years, or may be more, and by one of them only, Bishop Lesley, in 1578, was a definite habitat assigned to it:—“In Rossia quoque Louguhabria [Lochaber], atque aliis montanis locis” (De Origine Moribus et rebus gestis Scotorum. Romae: ed. 1675, p. 24). Pennant, during one of his tours in Scotland, found that it was then (1769) still to be met with in Glen Moriston and in The Chisholm’s country, whence he saw a cock-bird. We may infer that it became extinct about that time, since Robert Gray (Birds of the West of Scotland, p. 229) quotes the Rev. John Grant as writing in 1794: “The last seen in Scotland was in the woods of Strathglass about thirty-two years ago.” Of its existence in Ireland we have scarcely more details. If we may credit the Pavones sylvestres of Giraldus Cambrensis with being of this species, it was once abundant there, and Willughby (1678) was told that it was known in that kingdom as the “cock-of-the-wood.” A few other writers mention it by the same name, and John Rutty, in 1772, says (Nat. Hist. Dublin, i.p. 302) that “one was seen in the county of Leitrim about the year 1710, but they have entirely disappeared of late, by reason of the destruction of our woods.” Pennant also states that about 1760 a few were to be found about Thomastown in Tipperary, but no later evidence is forthcoming, and thus it would seem that the species was exterminated at nearly the same period in both Ireland and Scotland.

When the practice of planting was introduced, the restoration of this fine bird to both countries was attempted. In Ireland the trial, of which some particulars are given by J. Vaughan Thompson (Birds of Ireland, ii. 32), was made at Glengariff, but it seems to have utterly failed, whereas in Scotland, where it was begun at Taymouth, it finally succeeded, and the species is now not only firmly established, but is increasing in numbers and range. Mr L. Lloyd, the author of several excellent works on the wild sports and natural history of Scandinavia, supplied the stock from Sweden, but it must be always borne in mind that the original British race was wholly extinct, and no remains of it are known to exist in any museum.

This species is widely, though intermittently, distributed on the continent of Europe, from Lapland to the northern parts of Spain, Italy and Greece, but is always restricted to pine-forests, which alone afford it food in winter. Its bones have been found in the kitchen-middens of Denmark, proving that country to have once been clothed with woods of that kind. Its remains have also been recognized from the caves of Aquitaine. Its eastern or southern limits in Asia cannot be precisely given, but it certainly inhabits the forests of a great part of Siberia. On the Stannovoi Mountains, however, it is replaced by a distinct though nearly allied species, the T. urogalloides of Dr von Middendorff,2 which is smaller with a slenderer bill but longer tail.

The cock-of-the-wood is remarkable for his large size and dark plumage, with the breast metallic green. He is polygamous, and in spring mounts to the topmost bough of a tall tree, whence he challenges all comers by extraordinary sounds and gestures; while the hens, which are much smaller and mottled in colour, timidly abide below the result of the frequent duels, patiently submitting themselves to the victor. While this is going on it is the practice in many countries, though generally in defiance 251 of the law, for the so-called sportsman stealthily to draw nigh, and with well-aimed gun to murder the principal performer in the scene. The hen makes an artless nest on the ground, and lays therein from seven to nine or even more eggs. The young are able to fly soon after they are hatched, and towards the end of summer and beginning of autumn, from feeding on the fruit and leaves of the bilberries and other similar plants, which form the undercovert of the forests, get into excellent condition and become good eating. With the first heavy falls of snow they betake themselves to the trees, and then, feeding on the pine-leaves, their flesh speedily acquires so strong a flavour of turpentine as to be distasteful to most palates. The usual method of pursuing this species on the continent of Europe is by encouraging a trained dog to range the forest and spring the birds, which then perch on the trees; while he is baying at the foot their attention is so much attracted by him that they permit the near approach of his master, who thus obtains a more or less easy shot. A considerable number, however, are also snared. Hybrids are very frequently produced between the capercally and the black grouse (T. tetrix), and the offspring has been described by some authors under the name of T. medius, as though a distinct species.

CAPERN, EDWARD (1819-1894), English poet, was born at Tiverton, Devonshire, on the 21st of January 1819. From an early age he worked in a lace factory, but owing to failing eyesight he had to abandon this occupation in 1847 and he was in dire distress until he secured an appointment to be “the Rural Postman of Bideford,” by which name he is usually known. He occupied his leisure in writing occasional poetry which struck the popular fancy. Collected in a volume and published by subscription in 1856, it received the warm praise of the reviews and many distinguished people. Poems, by Edward Capern, was followed by Ballads and Songs (1858), The Devonshire Melodist (a collection of the author’s songs, some of them to his own music) and Wayside Warbles (1865), and resulted in a civil list pension being granted him by Lord Palmerston. He died on the 5th of June 1894.

CAPERNAUM (Καπερναούμ; probably, “the village of Naḥum”), an ancient city of Galilee. More than any other place, it was the home of Jesus after he began his mission; there he preached, called several of his disciples, and did many works, but without meeting with much response from the inhabitants, over whom he pronounced the heavy denunciation:—“And thou, Capernaum, which art exalted unto heaven, shalt be brought down to hell.” The site of the city has been a matter of much dispute,—one party, headed by Dr E. Robinson, maintaining an identification with Khan Minyeh at the north-west corner of the Sea of Galilee, and another, represented especially by Sir C.W. Wilson, supporting the claims of Tell Hum, midway between Khan Minyeh and the mouth of the Jordan. Khan Minyeh is beautifully situated in a “fertile plain formed by the retreat of the mountains about the middle of the western shore” of the Sea of Galilee. Its ruins are not very extensive, though they may have been despoiled for building the great Saracenic Khan from which they take their name. In the neighbourhood is a water-source, Ain et-Tābighah, an Arabic corruption of Heptapegon or Seven Springs (referred to by Josephus as being near Capernaum). Tell Hum lies about 3 m. north of Khan Minyeh, and its ruins, covering an area of “half a mile long by a quarter wide,” prove it to have been the site of no small town. It must be admitted that if it be not Capernaum it is impossible to say what ancient place it represents. But it is doubtful whether Tell Hūm can be considered as a corruption of Kefr Naḥum, the Semitic name which the Greek represents: and there is not here, as at Khan Minyeh, any spring that can be equated to the Heptapegon of Josephus. On the whole the probabilities of the two sites seem to balance, and it is practically impossible without further discoveries to decide between them. The sites of the neighbouring cities of Bethsaida and Chorazin are probably to be sought respectively at El-Bateiha, a grassy plain in the north-east corner of the lake, and at Kerazeh, 2 m. north of Tell Hum. According to the so-called Pseudo-Methodius there was a tradition that Antichrist would be born at Chorazin, educated at Bethsaida and rule at Capernaum—hence the curse of Jesus upon these cities.

CAPERS, the unexpanded flower-buds of Capparis spinosa, prepared with vinegar for use as a pickle. The caper plant is a trailing shrub, belonging to the Mediterranean region, resembling in habit the common bramble, and having handsome flowers of a pinkish white, with four petals, and numerous long tassel-like stamens. The leaves are simple and ovate, with spiny stipules. The plant is cultivated in Sicily and the south of France; and in commerce capers are valued according to the period at which the buds are gathered and preserved. The finest are the young tender buds called “nonpareil,” after which, gradually increasing in size and lessening in value, come “superfine,” “fine,” “capucin” and “capot.” Other species of Capparis are similarly employed in various localities, and in some cases the fruit is pickled.

CAPET, the name of a family to which, for nearly nine centuries, the kings of France, and many of the rulers of the most powerful fiefs in that country, belonged, and which mingled with several of the other royal races of Europe. The original significance of the name remains in dispute, but the first of the family to whom it was applied was Hugh, who was elected king of the Franks in 987. The real founder of the house, however, was Robert the Strong (q.v.), who received from Charles the Bald, king of the Franks, the countships of Anjou and Blois, and who is sometimes called duke, as he exercised some military authority in the district between the Seine and the Loire. According to Aimoin of Saint-Germain-des-Prés, and the chronicler, Richer, he was a Saxon, but historians question this statement. Robert’s two sons, Odo or Eudes, and Robert II., succeeded their father successively as dukes, and, in 887, some of the Franks chose Odo as their king. A similar step was taken, in 922, in the case of Robert II., this too marking the increasing irritation felt at the weakness of the Carolingian kings. When Robert died in 923, he was succeeded by his brother-in-law, Rudolph, duke of Burgundy, and not by his son Hugh, who is known in history as Hugh the Great, duke of France and Burgundy, and whose domain extended from the Loire to the frontiers of Picardy. When Louis V., king of the Franks, died in 987, the Franks, setting aside the Carolingians, passed over his brother Charles, and elected Hugh Capet, son of Hugh the Great, as their king, and crowned him at Reims. Avoiding the pretensions which had been made by the Carolingian kings, the Capetian kings were content, for a time, with a more modest position, and the story of the growth of their power belongs to the history of France. They had to combat the feudal nobility, and later, the younger branches of the royal house established in the great duchies, and the main reason for the permanence of their power was, perhaps, the fact that there were few minorities among them. The direct line ruled in France from 987 to 1328, when, at the death of King Charles IV., it was succeeded by the younger, or Valois, branch of the family. Philip VI., the first of the Valois kings, was a son of Charles I., count of Valois and grandson of King Philip III. (see Valois). The Capetian-Valois dynasty lasted until 1498, when Louis, duke of Orleans, became king as Louis XII., on the death of King Charles VIII. (see Orleans). Louis XII. dying childless, the house of Valois-Angoulême followed from Francis I. to the death of Henry III. in 1589 (see Angoulême), when the last great Capetian family, the Bourbons (q.v.) mounted the throne.

Scarcely second to the royal house is the branch to which belonged the dukes of Burgundy. In the 10th century the duchy of Burgundy fell into the hands of Hugh the Great, father of Hugh Capet, on whose death in 956 it passed to his son Otto, and, in 965, to his son Henry. In 1032 Robert, the second son of Robert the Pious, king of the Franks, and grandson of Hugh Capet, founded the first ducal house, which ruled until 1361. For two years the duchy was in the hands of the crown, but in 1363, the second ducal house, also Capetian, was founded by Philip the Bold, son of John II., king of France. This branch 252 of the Capetians is also distinguished by its union with the Habsburgs, through the marriage of Mary, daughter of Charles the Bold, duke of Burgundy, with Maximilian, afterwards the emperor Maximilian I. Of great importance also was the house of the counts of Anjou, which was founded in 1246, by Charles, son of the French king Louis VIII., and which, in 1360, was raised to the dignity of a dukedom (see Anjou). Members of this family sat upon the thrones of two kingdoms. The counts and dukes of Anjou were kings of Naples from 1265 to 1442. In 1308 Charles Robert of Anjou was elected king of Hungary, his claim being based on the marriage of his grandfather Charles II., king of Naples and count of Anjou, with Maria, daughter of Stephen V., king of Hungary. A third branch formed the house of the counts of Artois, which was founded in 1238 by Robert, son of King Louis VIII. This house merged in that of Valois in 1383, by the marriage of Margaret, daughter of Louis, count of Artois, with Philip the Bold, duke of Burgundy. The throne of Navarre was also filled by the Capetians. In 1284 Jeanne, daughter and heiress of Henry I., king of Navarre, married Philip IV., king of France, and the two kingdoms were united until Philip of Valois became king of France as Philip VI. in 1328, when Jeanne, daughter of King Louis X., and heiress of Navarre, married Philip, count of Evreux (see Navarre).

In the 13th century the throne of Constantinople was occupied by a branch of the Capetians. Peter, grandson of King Louis VI., obtained that dignity in 1217 as brother-in-law of the two previous emperors, Baldwin, count of Flanders, and his brother Henry. Peter was succeeded successively by his two sons, Robert and Baldwin, from whom in 1261 the empire was recovered by the Greeks.

The counts of Dreux, for two centuries and a half (1132-1377), and the counts of Evreux, from 1307 to 1425, also belonged to the family of the Capets,—other members of which worthy of mention are the Dunois and the Longuevilles, illegitimate branches of the house of Valois, which produced many famous warriors and courtiers.

CAPE TOWN, the capital of the Cape Province, South Africa, in 33° 56′ S., 18° 28′ E. It is at the north-west extremity of the Cape Peninsula on the south shore of Table Bay, is 6181 m. by sea from London and 957 by rail south-west of Johannesburg. Few cities are more magnificently situated. Behind the bay the massive wall of Table Mountain, 2 m. in length, rises to a height of over 3500 ft., while on the east and west projecting mountains enclose the plain in which the city lies. The mountain to the east, 3300 ft. high, which projects but slightly seawards, is the Devil’s Peak, that to the west the Lion’s Head (over 2000 ft. high), with a lesser height in front called the Lion’s Rump or Signal Hill. The city, at first confined to the land at the head of the bay, has extended all round the shores of the bay and to the lower spurs of Table Mountain.

The purely Dutch aspect which Cape Town preserved until the middle of the 19th century has disappeared. Nearly all the stucco-fronted brick houses, with flat roofs and cornices and wide spreading stoeps, of the early Dutch settlers have been replaced by shops, warehouses and offices in styles common to English towns. Of the many fine public buildings which adorn the city scarcely any date before 1860. The mixture of races among the inhabitants, especially the presence of numerous Malays, who on all festive occasions appear in gorgeous raiment, gives additional animation and colour to the street scenes. The mosques with their cupolas and minarets, and houses built in Eastern fashion contrast curiously with the Renaissance style of most of the modern buildings, the medieval aspect of the castle and the quaint appearance of the Dutch houses still standing.

Chief Public Buildings.—The castle stands near the shore at the head of the bay. Begun in 1666 its usefulness as a fortress has long ceased, but it serves to link the city to its past. West of the castle is a large oblong space, the Parade Ground. A little farther west, at the foot of the central jetty is a statue of Van Riebeek, the first governor of the Cape. In a line with the jetty is Adderley Street, and its continuation Government Avenue. Adderley Street and the avenue make one straight road a mile long, and at its end are “the Gardens,” as the suburbs built on the rising ground leading to Table Mountain are called. The avenue itself is fully half a mile long and is lined on either side with fine oak trees. In Adderley Street are the customs house and railway station, the Standard bank, the general post and telegraph offices, with a tower 120 ft. high, and the Dutch Reformed church. The church dates from 1699 and is the oldest church in South Africa. Of the original building only the clock tower (sent from Holland in 1727) remains. Government Avenue contains, on the east side, the Houses of Parliament, government house, a modernized Dutch building, and the Jewish synagogue; on the west side are the Anglican cathedral and grammar schools, the public library, botanic gardens, the museum and South African college. Many of these buildings are of considerable architectural merit, the material chiefly used in their construction being granite from the Paarl and red brick. The botanic gardens cover 14 acres, contain over 8000 varieties of trees and plants, and afford a magnificent view of Table Mountain and its companion heights. In the gardens, in front of the library is a statue of Sir George Grey, governor of the Cape from 1854 to 1861. The most valuable portion of the library is the 5000 volumes presented by Sir George Grey. In Queen Victoria Street, which runs along the west side of the gardens, are the Cape University buildings (begun in 1906), the law courts, City club and Huguenot memorial hall. The Anglican cathedral, begun in 1901 to replace an unpretentious building on the same site, is dedicated to St George. It lies between the library and St George’s Street, in which are the chief newspaper offices, and premises of the wholesale merchants. West of St George’s Street is Greenmarket Square, the centre of the town during the Dutch period. From the balcony of the town house, which overlooks the square, proclamations were read to the burghers, summoned to the spot by the ringing of the bell in the small-domed tower. Still farther west, in Riebeek Square, is the old slave market, now used as a church and school for coloured people.

Facing the north side of the Parade Ground are the handsome municipal buildings, completed in 1906. The most conspicuous feature is the clock tower and belfry, 200 ft. high. The hall is 130 ft. by 62, and 55 ft. high. Opposite the main entrance is a statue of Edward VII. by William Goscombe John, unveiled in 1905. The opera house occupies the north-west corner of the Parade Ground. Plein Street, which leads south from the Parade Ground, is noted for its cheap shops, largely patronized on Saturday nights by the coloured inhabitants. In Sir Lowry Road, the chief eastern thoroughfare, is the large vegetable and fruit market. Immediately west of the harbour are the convict station and Somerset hospital. They are built at the town end of Greenpoint Common, the open space at the foot of Signal Hill. Cape Town is provided with an excellent water supply and an efficient drainage system.

The Suburbs.—The suburbs of Cape Town, for natural beauty of position, are among the finest in the world. On the west they extend about 3 m., by Green Point to Sea Point, between the sea and the foot of the Lion’s Rump; on the east they run round the foot of the Devil’s Peak, by Woodstock, Mowbray, Rondebosch, Newlands, Claremont, &c., to Wynberg, a distance of 7 m. Though these are managed by various municipalities, there is practically no break in the buildings for the whole distance. All the parts are connected by the suburban railway service, and by an electric tramway system. A tramway also runs from the town over the Kloof, or pass between Table Mountain and the Lion’s Head, to Camp’s Bay, on the west coast south of Sea Point, to which place it is continued, the tramway thus completely circling the Lion’s Head and Signal Hill. Of the suburbs mentioned, Green Point and Sea Point are seaside resorts, Woodstock being both a business and residential quarter. Woodstock covers the ground on which the British, in 1806, defeated the Dutch, and contains the house in which the articles of capitulation were signed. Another seaside suburb is Milnerton on the north-east shores of Table Bay at the mouth of the Diep river. Near Maitland, and 3 m. from the city, is the Cape Town observatory, built in 253 1820 and maintained by the British government. Rondebosch, 5 m. from the city, contains some of the finest of the Dutch mansions in South Africa. Less than a mile from the station is Groote Schuur, a typical specimen of the country houses built by the Dutch settlers in the 17th century. The house was the property of Cecil Rhodes, and was bequeathed by him for the use of the prime minister of Federated South Africa. The grounds of the estate extend up the slopes of Table Mountain. At Newlands is Bishop’s Court, the home of the archbishop of Cape Town. More distant suburbs to the south-east are Constantia, with a famous Dutch farm-house and wine farm, and Muizenberg and Kalk Bay, the two last villages on the shore of False Bay. At Muizenberg Cecil Rhodes died, 1902. Facing the Atlantic is Hout’s Bay, 10 m. south-south-west of Wynberg.

Most of the suburbs and the city itself are exposed to the south-east winds which, passing over the flats which join the Cape Peninsula to the mainland, reach the city sand-laden. From its bracing qualities this wind, which blows in the summer, is known as the “Cape Doctor.” During its prevalence Table Mountain is covered by a dense whitish-grey cloud, overlapping its side like a tablecloth.

The Harbour.—Table Bay, 20 m. wide at its entrance, is fully exposed to north and north-west gales. The harbour works, begun in 1860, afford sheltered accommodation for a large number of vessels. From the west end of the bay a breakwater extends north-east for some 4000 ft. East of the breakwater and parallel to it for 2700 ft. is the South pier. From breakwater and pier arms project laterally. In the area enclosed are the Victoria basin, covering 64 acres, the Alfred basin of 8½ acres, a graving dock 529 ft. long and a patent slip for vessels up to 1500 tons. There is good anchorage outside the Victoria basin under the lee of the breakwater, and since 1904 the foreshore east of the south pier has been reclaimed and additional wharfage provided. Altogether there are 2½ m. of quay walls, the wharfs being provided with electrical cranage. Cargo can be transferred direct from the ship into railway trucks. Vessels of the deepest draught can enter into the Victoria basin, the depth of water at low tide ranging from 24 to 36 ft.

Trade and Communication.—The port has a practical monopoly of the passenger traffic between the Cape and England. Several lines of steamers—chiefly British and German—maintain regular communication with Europe, the British mail boats taking sixteen days on the journey. By its railway connexions Cape Town affords the quickest means of reaching, from western Europe, every other town in South Africa. In the import trade Cape Town is closely rivalled by Port Elizabeth, but its export trade, which includes diamonds and bar gold, is fully 70% of that of the entire colony. In 1898, the year before the beginning of the Anglo-Boer war, the volume of trade was:—Imports £5,128,292, exports £15,881,952. In 1904, two years after the conclusion of the war the figures were:—imports £9,070,757; exports £17,471,760. In 1907 during a period of severe and prolonged trade depression the imports had fallen to £5,263,930, but the exports owing entirely to the increased output of gold from the Rand mines had increased to £37,994,658; gold and diamonds represented over £37,000,000 of this total. The tonnage of ships entering the harbour in 1887 was 801,033. In 1904 it had risen to 4,846,012 and in 1907 was 4,671,146. The trade of the port in tons was 1,276,350 in 1899 and 1,413,471 in 1904. In 1907 it had fallen to 658,721.

Defence.—Cape Town, being in the event of the closing of the Suez Canal on the main route of ships from Europe to the East, is of considerable strategic importance. It is defended by several batteries armed with modern heavy guns. It is garrisoned by Imperial and local troops, and is connected by railway with the naval station at Simon’s Town on the east of the Cape Peninsula.

Population.—The Cape electoral division, which includes Cape Town, had in 1865 a population of 50,064, in 1875 57,319, in 1891 97,238, and in 1904 213,167, of whom 120,475 were whites. Cape Town itself had a population in 1875 of 33,000, in 1891 of 51,251 and in 1904 of 77,668. Inclusive of the nearer suburbs the population was 78,866 in 1891 and 170,083 in 1904. Of the inhabitants of the city proper 44,203 were white (1904). Of the coloured inhabitants 6561 were Malays; the remainder being chiefly of mixed blood. The most populous suburbs in 1904 were Woodstock with 28,990 inhabitants, and Wynberg with 18,477.

History and Local Government.—Cape Town was founded in 1652 by settlers sent from Holland by the Netherlands East India Co., under Jan van Riebeek. It came definitely into the possession of Great Britain in 1806. Its political history is indistinguishable from that of Cape Colony (q.v.). The town was granted municipal institutions in 1836. (Among the councillors returned at the election of 1904 was Dr Abdurrahman, a Mahommedan and a graduate of Edinburgh, this being, it is believed, the first instance of the election of a man of colour to any European representative body in South Africa.) The municipality owns the water and lighting services. The municipal rating value was, in 1880 £2,054,204, in 1901 £9,475,260, in 1908 (when the rate levied was 3d. in the £) £14,129,439. The total rateable value of the suburbs, not included in the above figures, is over £8,000,000. Rates are based on capital, not annual, value. The control of the port is vested in the Harbour and Railway Board of the Union.

Cape Town is the seat of the legislature of the Union of South Africa, of the provincial government, of the provincial division of the Supreme Court of South Africa, and of the Cape University; also of an archbishop of the Anglican and a bishop of the Roman Catholic churches.

CAPE VERDE ISLANDS (Ilhas do Caba Verde), an archipelago belonging to Portugal; off the West African coast, between 17° 13′ and 14° 47′ N. and 22° 40′ and 25° 22′ W. Pop. (1905) about 138,620; area, 1475 sq. m. The archipelago consists of ten islands:—Santo Antão (commonly miswritten St Antonio), São Vicente, Santa Luzia, São Nicolao, Sal, Boa Vista, Maio, São Thiago (the St Jago of the English), Fogo, and Brava, besides four uninhabited islets. It forms a sort of broken crescent, with the concavity towards the west. The last four islands constitute the leeward (Sotavento) group and the other six the windward (Barlavento). The distance between the coast of Africa and the nearest island (Boa Vista) is about 300 m. The islands derive their name, frequently but erroneously written “Cape Verd,” or “Cape de Verd” Islands, from the African promontory off which they lie, known as Cape Verde, or the Green Cape. The entire archipelago is of volcanic origin, and on the island of Fogo there is an active volcano. No serious eruption has taken place since 1680, and the craters from which the streams of basalt issued have lost their outline.

254

Climate.—The atmosphere of the islands is generally hazy, especially in the direction of Africa. With occasional exceptions during summer and autumn, the north-east trade is the prevailing wind, blowing most strongly from November to May. The rainy season is during August, September and October, when there is thunder and a light variable wind from south-east or south-west. The Harmattan, a very dry east wind from the African continent, occasionally makes itself felt. The heat of summer is high, the thermometer ranging from 80° to 90° Fahr. near the sea. The unhealthy season is the period during and following the rains, when vegetation springs up with surprising rapidity, and there is much stagnant water, poisoning the air on the lower grounds. Remittent fevers are then common. The people of all the islands are also subject in May to an endemic of a bilious nature called locally levadias, but the cases rarely assume a dangerous form, and recovery is usually attained in three or four days without medical aid. On some of the islands rain has occasionally not fallen for three years. The immediate consequence is a failure of the crops, and this is followed by the death of great numbers from starvation, or the epidemics which usually break out afterwards.

Flora.—Owing largely to the widespread destruction of timber for fuel, and to the frequency of drought, the flora of the islands is poor when compared with that of the Canaries, the Azores or Madeira. It is markedly tropical in character; and although some seventy wild-flowers, grasses, ferns, &c., are peculiar to the archipelago, the majority of plants are those found on the neighbouring African littoral. Systematic afforestation has not been attempted, but the Portuguese have introduced a few trees, such as the baobab, eucalyptus and dragon-tree, besides many plants of economic value. Coffee-growing, an industry dating from 1790, is the chief resource of the people of Santo Antão, Fogo and São Thiago; maize, millet, sugar-cane, manioc, excellent oranges, pumpkins, sweet potatoes, and, to a less extent, tobacco and cotton are produced. On most of the islands coco-nut and date palms, tamarinds and bananas may be seen; orchil is gathered; and indigo and castor-oil are produced. Of considerable importance is the physic-nut (Jatropha curcas), which is exported.

Fauna.—Quails are found in all the islands; rabbits in Boa Vista, São Thiago and Fogo; wild boars in São Thiago. Both black and grey rats are common. Goats, horses and asses are reared, and goatskins are exported. The neighbouring sea abounds with fish, and coral fisheries are carried on by a colony of Neapolitans in São Thiago. Turtles come from the African coast to lay their eggs on the sandy shores. The Ilheu Branco, or White Islet, between São Nicolao and Santa Luzia, is remarkable as containing a variety of puffin unknown elsewhere, and a species of large lizard (Macroscinctus coctei) which feeds on plants.

Inhabitants.—The first settlers on the islands imported negro slaves from the African coast. Slavery continued in full force until 1854, when the Portuguese government freed the public slaves, and ameliorated the conditions of private ownership. In 1857 arrangements were made for the gradual abolition of slavery, and by 1876 the last slave had been liberated. The transportation of convicts from Portugal, a much-dreaded punishment, was continued until the closing years of the 19th century. It was the coexistence of these two forms of servitude, even more than the climate, which prevented any large influx of Portuguese colonists. Hence the blacks and mulattoes far outnumber the white inhabitants. They are, as a rule, taller than the Portuguese, and are of fine physique, with regular features but woolly hair. Slavery and the enervating climate have left their mark on the habits of the people, whose indolence and fatalism are perhaps their most obvious qualities. Their language is a bastard Portuguese, known as the lingua creoula. Their religion is Roman Catholicism, combined with a number of pagan beliefs and rites, which are fostered by the curandeiros or medicine men. These superstitions tend to disappear gradually before the advance of education, which has progressed considerably since 1867, when the first school, a lyceum, was opened in Ribeira Brava, the capital of São Nicolao. On all the inhabited islands, except Santa Luzia, there are churches and primary schools, conducted by the government or the priests. The children of the wealthier classes are sent to Lisbon for their education.

Government.—The archipelago forms one of the foreign provinces of Portugal, and is under the command of a governor-in-chief appointed by the crown. There are two principal judges, one for the windward and another for the leeward group, the former with his residence at São Nicolao, and the latter at Praia; and each island has a military commandant, a few soldiers, and a number of salaried officials, such as police, magistrates and custom-house directors. There is also an ecclesiastical establishment, with a bishop, dean and canons.

Industries.—The principal industries, apart from agriculture, are the manufacture of sugar, spirits, salt, cottons and straw hats and fish-curing. The average yearly value of the exports is about £60,000; that of the imports (including £200,000 for coal), about £350,000. The most important of the exports are coffee, physic-nuts, millet, sugar, spirits, salt, live animals, skins and fish. This trade is principally carried on with Lisbon and the Portuguese possessions on the west coast of Africa, and with passing vessels. The imports consist principally of coal, textiles, food-stuffs, wine, metals, tobacco, machinery, pottery and vegetables. Over 3000 vessels, with a total tonnage exceeding 3,500,000, annually enter the ports of the archipelago; the majority call at Mindello, on São Vicente, for coal, and do not receive or discharge any large quantities of cargo.

History.—The earliest known discovery of the islands was made in 1456 by the Venetian captain Alvise Cadamosto (q.v.), who had entered the service of Prince Henry the Navigator. The archipelago was granted by King Alphonso V. of Portugal to his brother, Prince Ferdinand, whose agents completed the work of discovery. Ferdinand was an absolute monarch, exercising a commercial monopoly. In 1461 he sent an expedition to recruit slaves on the coast of Guinea and thus to people the islands, which were almost certainly uninhabited at the time. On his death in 1470 his privileges reverted to the crown, and were bestowed by John II. on Prince Emanuel, by whose accession to the throne in 1495 the archipelago finally became part of the royal dominions. Its population and importance rapidly increased; its first bishop was consecrated in 1532, its first governor-general appointed about the end of the century. It was enriched by the frequent visits of Portuguese fleets, on their return to Europe laden with treasure from the East, and by the presence of immigrants from Madeira, who introduced better agricultural methods and several new industries, such as dyeing and distillation of spirits. The failure to maintain an equal rate of progress in the 18th and 19th centuries was due partly to drought, famine and disease—in particular, to the famines of 1730-1733 and 1831-1833—and partly to gross misgovernment by the Portuguese officials.

CAPGRAVE, JOHN (1393-1464), English chronicler and hagiologist, was born at Lynn in Norfolk on the 21st of April 1393. He became a priest, took the degree of D.D. at Oxford, where he lectured on theology, and subsequently joined the order of Augustinian hermits. Most of his life he spent in the house of the order at Lynn, of which he probably became prior; he was certainly provincial of his order in England, which involved visits to other friaries, and he made at least one journey to Rome. He died on the 12th of August 1464.

Capgrave was an indefatigable student, and was reputed one of the most learned men of his age. The bulk of his works are theological: sermons, commentaries and lives of saints. His reputation as a hagiologist rests on his Nova legenda Angliae, or Catalogus of the English saints, but this was no more than a recension of the Sanctilogium which the chronicler John of Tinmouth, a monk of St Albans, had completed in 1366, which in its turn was largely borrowed from the Sanctilogium of Guido, abbot of St Denis. The Nova legenda was printed by Wynkyn de Worde in 1516 and again in 1527. Capgrave’s historical works are The Chronicle of England (from the Creation to 1417), written in English and unfinished at his death, and the Liber de illustribus Henricis, completed between 1446 and 1453. The latter is a collection of lives of German emperors (918-1198), English kings (1100-1446) and other famous Henries in various parts of the world (1031-1406). The portion devoted to Henry VI. of England is a contemporary record, but consists mainly of ejaculations in praise of the pious king. The accounts of the 256 other English Henries are transferred from various well-known chroniclers. The Chronicle was edited for the “Rolls” Series by Francis Charles Hingeston (London, 1858); the Liber de illustrious Henricis was edited (London, 1858) for the same series by F.C. Hingeston, who published an English translation the same year. The editing of both the works is very uncritical and bad.

CAP HAITIEN, Cape Haïtien or Haytien, a seaport of Haiti West Indies. Pop. about 15,000. It is situated on the north coast, 90 m. N. of Port au Prince, in 19° 46′ N. and 72° 14′ W. Its original Indian name was Guarico, and it has been known, at various times, as Cabo Santo, Cap Français and Cape Henri, while throughout Haiti it is always called Le Cap. It is the most picturesque town in the republic, and the second in importance. On three sides it is hemmed in by lofty mountains, while on the fourth it overlooks a safe and commodious harbour. Under the French rule it was the capital of the colony, and its splendour, wealth and luxury earned for it the title of the “Paris of Haiti.” It was then the see of an archbishop and possessed a large and flourishing university. The last remains of its former glory were destroyed by the earthquake of 1842 and the British bombardment of 1865. Although now but a collection of squalid wooden huts, with here and there a well-built warehouse, it is the centre of a thriving district and does a large export trade. It was founded by the Spaniards about the middle of the 17th century, and in 1687 received a large French colony. In 1695 it was taken and burned by the British, and in 1791 it suffered the same fate at the hands of Toussaint L’Ouverture. It then became the capital of King Henri Christophe’s dominions, but since his fall has suffered severely in numerous revolutions.

CAPILLARY ACTION.1 A tube, the bore of which is so small that it will only admit a hair (Lat. capilla), is called a capillary tube. When such a tube of glass, open at both ends, is placed vertically with its lower end immersed in water, the water is observed to rise in the tube, and to stand within the tube at a higher level than the water outside. The action between the capillary tube and the water has been called capillary action, and the name has been extended to many other phenomena which have been found to depend on properties of liquids and solids similar to those which cause water to rise in capillary tubes.

The forces which are concerned in these phenomena are those which act between neighbouring parts of the same substance, and which are called forces of cohesion, and those which act between portions of matter of different kinds, which are called forces of adhesion. These forces are quite insensible between two portions of matter separated by any distance which we can directly measure. It is only when the distance becomes exceedingly small that these forces become perceptible. G.H. Quincke (Pogg. Ann. cxxxvii. p. 402) made experiments to determine the greatest distance at which the effect of these forces is sensible, and he found for various substances distances about the twenty-thousandth part of a millimetre.

Historical.—According to J.C. Poggendorff (Pogg. Ann. ci. p. 551), Leonardo da Vinci must be considered as the discoverer of capillary phenomena, but the first accurate observations of the capillary action of tubes and glass plates were made by Francis Hawksbee (Physico-Mechanical Experiments, London, 1709, pp. 139-169; and Phil. Trans., 1711 and 1712), who ascribed the action to an attraction between the glass and the liquid. He observed that the effect was the same in thick tubes as in thin, and concluded that only those particles of the glass which are very near the surface have any influence on the phenomenon. Dr James Jurin (Phil. Trans., 1718, p. 739, and 1719, p. 1083) showed that the height at which the liquid is suspended depends on the section of the tube at the surface of the liquid, and is independent of the form of the lower part of the tube. He considered that the suspension of the liquid is due to “the attraction of the periphery or section of the surface of the tube to which the upper surface of the water is contiguous and coheres.” From this he showed that the rise of the liquid in tubes of the same substance is inversely proportional to their radii. Sir Isaac Newton devoted the 31st query in the last edition of his Opticks to molecular forces, and instanced several examples of the cohesion of liquids, such as the suspension of mercury in a barometer tube at more than double the height at which it usually stands. This arises from its adhesion to the tube, and the upper part of the mercury sustains a considerable tension, or negative pressure, without the separation of its parts. He considered the capillary phenomena to be of the same kind, but his explanation is not sufficiently explicit with respect to the nature and the limits of the action of the attractive force.

It is to be observed that, while these early speculators ascribe the phenomena to attraction, they do not distinctly assert that this attraction is sensible only at insensible distances, and that for all distances which we can directly measure the force is altogether insensible. The idea of such forces, however, had been distinctly formed by Newton, who gave the first example of the calculation of the effect of such forces in his theorem on the alteration of the path of a light-corpuscle when it enters or leaves a dense body.

Alexis Claude Clairault (Théorie de la figure de la terre, Paris, 1808, pp. 105, 128) appears to have been the first to show the necessity of taking account of the attraction between the parts of the fluid itself in order to explain the phenomena. He did not, however, recognize the fact that the distance at which the attraction is sensible is not only small but altogether insensible. J.A. von Segner (Comment. Soc. Reg. Götting, i. (1751) p. 301) introduced the very important idea of the surface-tension of liquids, which he ascribed to attractive forces, the sphere of whose action is so small “ut nullo adhuc sensu percipi potuerit.” In attempting to calculate the effect of this surface-tension in determining the form of a drop of the liquid, Segner took account of the curvature of a meridian section of the drop, but neglected the effect of the curvature in a plane at right angles to this section.

The idea of surface-tension introduced by Segner had a most important effect on the subsequent development of the theory. We may regard it as a physical fact established by experiment in the same way as the laws of the elasticity of solid bodies. We may investigate the forces which act between finite portions of a liquid in the same way as we investigate the forces which act between finite portions of a solid. The experiments on solids lead to certain laws of elasticity expressed in terms of coefficients, the values of which can be determined only by experiments on each particular substance. Various attempts have also been made to deduce these laws from particular hypotheses as to the action between the molecules of the elastic substance. We may therefore regard the theory of elasticity as consisting of two parts. The first part establishes the laws of the elasticity of a finite portion of the solid subjected to a homogeneous strain, and deduces from these laws the equations of the equilibrium and motion of a body subjected to any forces and displacements. The second part endeavours to deduce the facts of the elasticity of a finite portion of the substance from hypotheses as to the motion of its constituent molecules and the forces acting between them. In like manner we may by experiment ascertain the general fact that the surface of a liquid is in a state of tension similar to that of a membrane stretched equally in all directions, and prove that this tension depends only on the nature and temperature of the liquid and not on its form, and from this as a secondary physical principle we may deduce all the phenomena of capillary action. This is one step of the investigation. The next step is to deduce this surface-tension from a hypothesis as to the molecular constitution of the liquid and of the bodies that surround it. The scientific importance of this step is to be measured by the degree of insight which it affords or promises into the molecular constitution of real bodies by the suggestion of experiments by which we may discriminate between rival molecular theories.

257

In 1756 J.G. Leidenfrost (De aquae communis nonnullis qualitatibus tractatus, Duisburg) showed that a soap-bubble tends to contract, so that if the tube with which it was blown is left open the bubble will diminish in size and will expel through the tube the air which it contains. He attributed this force, however, not to any general property of the surfaces of liquids, but to the fatty part of the soap which he supposed to separate itself from the other constituents of the solution, and to form a thin skin on the outer face of the bubble.

In 1787 Gaspard Monge (Mémoires de l’Acad. des Sciences, 1787, p. 506) asserted that “by supposing the adherence of the particles of a fluid to have a sensible effect only at the surface itself and in the direction of the surface it would be easy to determine the curvature of the surfaces of fluids in the neighbourhood of the solid boundaries which contain them; that these surfaces would be linteariae of which the tension, constant in all directions, would be everywhere equal to the adherence of two particles, and the phenomena of capillary tubes would then present nothing which could not be determined by analysis.” He applied this principle of surface-tension to the explanation of the apparent attractions and repulsions between bodies floating on a liquid.

In 1802 John Leslie (Phil. Mag., 1802, vol. xiv. p. 193) gave the first correct explanation of the rise of a liquid in a tube by considering the effect of the attraction of the solid on the very thin stratum of the liquid in contact with it. He did not, like the earlier speculators, suppose this attraction to act in an upward direction so as to support the fluid directly. He showed that the attraction is everywhere normal to the surface of the solid. The direct effect of the attraction is to increase the pressure of the stratum of the fluid in contact with the solid, so as to make it greater than the pressure in the interior of the fluid. The result of this pressure if unopposed is to cause this stratum to spread itself over the surface of the solid as a drop of water is observed to do when placed on a clean horizontal glass plate, and this even when gravity opposes the action, as when the drop is placed on the under surface of the plate. Hence a glass tube plunged into water would become wet all over were it not that the ascending liquid film carries up a quantity of other liquid which coheres to it, so that when it has ascended to a certain height the weight of the column balances the force by which the film spreads itself over the glass. This explanation of the action of the solid is equivalent to that by which Gauss afterwards supplied the defect of the theory of Laplace, except that, not being expressed in terms of mathematical symbols, it does not indicate the mathematical relation between the attraction of individual particles and the final result. Leslie’s theory was afterwards treated according to Laplace’s mathematical methods by James Ivory in the article on capillary action, under “Fluids, Elevation of,” in the supplement to the fourth edition of the Encyclopaedia Britannica, published in 1819.

In 1804 Thomas Young (Essay on the “Cohesion of Fluids,” Phil. Trans., 1805, p. 65) founded the theory of capillary phenomena on the principle of surface-tension. He also observed the constancy of the angle of contact of a liquid surface with a solid, and showed how from these two principles to deduce the phenomena of capillary action. His essay contains the solution of a great number of cases, including most of those afterwards solved by Laplace, but his methods of demonstration, though always correct, and often extremely elegant, are sometimes rendered obscure by his scrupulous avoidance of mathematical symbols. Having applied the secondary principle of surface-tension to the various particular cases of capillary action, Young proceeded to deduce this surface-tension from ulterior principles. He supposed the particles to act on one another with two different kinds of forces, one of which, the attractive force of cohesion, extends to particles at a greater distance than those to which the repulsive force is confined. He further supposed that the attractive force is constant throughout the minute distance to which it extends, but that the repulsive force increases rapidly as the distance diminishes. He thus showed that at a curved part of the surface, a superficial particle would be urged towards the centre of curvature of the surface, and he gave reasons for concluding that this force is proportional to the sum of the curvatures of the surface in two normal planes at right angles to each other.

The subject was next taken up by Pierre Simon Laplace (Mécanique céleste, supplement to the tenth book, pub. in 1806). His results are in many respects identical with those of Young, but his methods of arriving at them are very different, being conducted entirely by mathematical calculations. The form into which he threw his investigation seems to have deterred many able physicists from the inquiry into the ulterior cause of capillary phenomena, and induced them to rest content with deriving them from the fact of surface-tension. But for those who wish to study the molecular constitution of bodies it is necessary to study the effect of forces which are sensible only at insensible distances; and Laplace has furnished us with an example of the method of this study which has never been surpassed. Laplace investigated the force acting on the fluid contained in an infinitely slender canal normal to the surface of the fluid arising from the attraction of the parts of the fluid outside the canal. He thus found for the pressure at a point in the interior of the fluid an expression of the form

p = K + ½H(1/R + 1/R′),

where K is a constant pressure, probably very large, which, however, does not influence capillary phenomena, and therefore cannot be determined from observation of such phenomena; H is another constant on which all capillary phenomena depend; and R and R’ are the radii of curvature of any two normal sections of the surface at right angles to each other.

In the first part of our own investigation we shall adhere to the symbols used by Laplace, as we shall find that an accurate knowledge of the physical interpretation of these symbols is necessary for the further investigation of the subject. In the Supplement to the Theory of Capillary Action, Laplace deduced the equation of the surface of the fluid from the condition that the resultant force on a particle at the surface must be normal to the surface. His explanation, however, of the rise of a liquid in a tube is based on the assumption of the constancy of the angle of contact for the same solid and fluid, and of this he has nowhere given a satisfactory proof. In this supplement Laplace gave many important applications of the theory, and compared the results with the experiments of Louis Joseph Gay Lussac.

The next great step in the treatment of the subject was made by C.F. Gauss (Principia generalia Theoriae Figurae Fluidorum in statu Aequilibrii, Göttingen, 1830, or Werke, v. 29, Göttingen, 1867). The principle which he adopted is that of virtual velocities, a principle which under his hands was gradually transforming itself into what is now known as the principle of the conservation of energy. Instead of calculating the direction and magnitude of the resultant force on each particle arising from the action of neighbouring particles, he formed a single expression which is the aggregate of all the potentials arising from the mutual action between pairs of particles. This expression has been called the force-function. With its sign reversed it is now called the potential energy of the system. It consists of three parts, the first depending on the action of gravity, the second on the mutual action between the particles of the fluid, and the third on the action between the particles of the fluid and the particles of a solid or fluid in contact with it.

The condition of equilibrium is that this expression (which we may for the sake of distinctness call the potential energy) shall be a minimum. This condition when worked out gives not only the equation of the free surface in the form already established by Laplace, but the conditions of the angle of contact of this surface with the surface of a solid.

Gauss thus supplied the principal defect in the great work of Laplace. He also pointed out more distinctly the nature of the assumptions which we must make with respect to the law of action of the particles in order to be consistent with observed phenomena. He did not, however, enter into the explanation of particular phenomena, as this had been done already by Laplace, but he pointed out to physicists the advantages of the 258 method of Segner and Gay Lussac, afterwards carried out by Quincke, of measuring the dimensions of large drops of mercury on a horizontal or slightly concave surface, and those of large bubbles of air in transparent liquids resting against the under side of a horizontal plate of a substance wetted by the liquid.

In 1831 Siméon Denis Poisson published his Nouvelle Théorie de l’action capillaire. He maintained that there is a rapid variation of density near the surface of a liquid, and he gave very strong reasons, which have been only strengthened by subsequent discoveries, for believing that this is the case. He proceeded to an investigation of the equilibrium of a fluid on the hypothesis of uniform density, and arrived at the conclusion that on this hypothesis none of the observed capillary phenomena would take place, and that, therefore, Laplace’s theory, in which the density is supposed uniform, is not only insufficient but erroneous. In particular he maintained that the constant pressure K, which occurs in Laplace’s theory, and which on that theory is very large, must be in point of fact very small, but the equation of equilibrium from which he concluded this is itself defective. Laplace assumed that the liquid has uniform density, and that the attraction of its molecules extends to a finite though insensible distance. On these assumptions his results are certainly right, and are confirmed by the independent method of Gauss, so that the objections raised against them by Poisson fall to the ground. But whether the assumption of uniform density be physically correct is a very different question, and Poisson rendered good service to science in showing how to carry on the investigation on the hypothesis that the density very near the surface is different from that in the interior of the fluid.

The result, however, of Poisson’s investigation is practically equivalent to that already obtained by Laplace. In both theories the equation of the liquid surface is the same, involving a constant H, which can be determined only by experiment. The only difference is in the manner in which this quantity H depends on the law of the molecular forces and the law of density near the surface of the fluid, and as these laws are unknown to us we cannot obtain any test to discriminate between the two theories.

We have now described the principal forms of the theory of capillary action during its earlier development. In more recent times the method of Gauss has been modified so as to take account of the variation of density near the surface, and its language has been translated in terms of the modern doctrine of the conservation of energy.2

J.A.F. Plateau (Statique expérimentale et théorique des liquides), who made elaborate study of the phenomena of surface-tension, adopted the following method of getting rid of the effects of gravity. He formed a mixture of alcohol and water of the same density as olive oil, and then introduced a quantity of oil into the mixture. It assumes the form of a sphere under the action of surface-tension alone. He then, by means of rings of iron-wire, disks and other contrivances, altered the form of certain parts of the surface of the oil. The free portions of the surface then assume new forms depending on the equilibrium of surface-tension. In this way he produced a great many of the forms of equilibrium of a liquid under the action of surface-tension alone, and compared them with the results of mathematical investigation. He also greatly facilitated the study of liquid films by showing how to form a liquid, the films of which will last for twelve or even for twenty-four hours. The debt which science owes to Plateau is not diminished by the fact that, while investigating these beautiful phenomena, he never himself saw them, having lost his sight in about 1840.

G.L. van der Mensbrugghe (Mém. de l’Acad. Roy. de Belgique, xxxvii., 1873) devised a great number of beautiful illustrations of the phenomena of surface-tension, and showed their connexion with the experiments of Charles Tomlinson on the figures formed by oils dropped on the clean surface of water.

Athanase Dupré in his 5th, 6th and 7th Memoirs on the Mechanical Theory of Heat (Ann. de Chimie et de Physique, 1866-1868) applied the principles of thermodynamics to capillary phenomena, and the experiments of his son Paul were exceedingly ingenious and well devised, tracing the influence of surface-tension in a great number of very different circumstances, and deducing from independent methods the numerical value of the surface-tension. The experimental evidence which Dupré obtained bearing on the molecular structure of liquids must be very valuable, even if our present opinions on this subject should turn out to be erroneous.

F.H.R. Lüdtge (Pogg. Ann. cxxxix. p. 620) experimented on liquid films, and showed how a film of a liquid of high surface-tension is replaced by a film of lower surface-tension. He also experimented on the effects of the thickness of the film, and came to the conclusion that the thinner a film is, the greater is its tension. This result, however, was tested by Van der Mensbrugghe, who found that the tension is the same for the same liquid whatever be the thickness, as long as the film does not burst. [The continued coexistence of various thicknesses, as evidenced by the colours in the same film, affords an instantaneous proof of this conclusion.] The phenomena of very thin liquid films deserve the most careful study, for it is in this way that we are most likely to obtain evidence by which we may test the theories of the molecular structure of liquids.

Sir W. Thomson (afterwards Lord Kelvin) investigated the effect of the curvature of the surface of a liquid on the thermal equilibrium between the liquid and the vapour in contact with it. He also calculated the effect of surface-tension on the propagation of waves on the surface of a liquid, and determined the minimum velocity of a wave, and the velocity of the wind when it is just sufficient to disturb the surface of still water.

Theory of Capillary Action

When two different fluids are placed in contact, they may either diffuse into each other or remain separate. In some cases diffusion takes place to a limited extent, after which the resulting mixtures do not mix with each other. The same substance may be able to exist in two different states at the same temperature and pressure, as when water and its saturated vapour are contained in the same vessel. The conditions under which the thermal and mechanical equilibrium of two fluids, two mixtures, or the same substance in two physical states in contact with each other, is possible belong to thermodynamics. All that we have to observe at present is that, in the cases in which the fluids do not mix of themselves, the potential energy of the system must be greater when the fluids are mixed than when they are separate.

It is found by experiment that it is only very close to the bounding surface of a liquid that the forces arising from the mutual action of its parts have any resultant effect on one of its particles. The experiments of Quincke and others seem to show that the extreme range of the forces which produce capillary action lies between a thousandth and a twenty-thousandth part of a millimetre.

We shall use the symbol ε to denote this extreme range, beyond which the action of these forces may be regarded as insensible. If χ denotes the potential energy of unit of mass of the substance, we may treat χ as sensibly constant except within a distance ε of the bounding surface of the fluid. In the interior of the fluid it has the uniform value χ0. In like manner the density, ρ, is sensibly equal to the constant quantity ρ0, which is its value in the interior of the liquid, except within a distance ε of the bounding surface. Hence if V is the volume of a mass M of liquid bounded by a surface whose area is S, the integral

M = ∫∫∫ ρ dxdydz,     (1)

where the integration is to be extended throughout the volume 259 V, may be divided into two parts by considering separately the thin shell or skin extending from the outer surface to a depth ε, within which the density and other properties of the liquid vary with the depth, and the interior portion of the liquid within which its properties are constant.

Since ε is a line of insensible magnitude compared with the dimensions of the mass of liquid and the principal radii of curvature of its surface, the volume of the shell whose surface is S and thickness ε will be Sε, and that of the interior space will be V − Sε.

The volume of one of these shells will be Sdν. Its mass will be Sρdν. The mass of the whole shell will therefore be S∫ε0 ρdν, and that of the interior part of the liquid (V − Sε)ρ0. We thus find for the whole mass of the liquid

M = V ρ0 − S ∫ε0(ρ0 − ρ) dν.    (2)

To find the potential energy we have to integrate

∫∫∫ χρ dxdydz.    (3)

Substituting χρ for ρ in the process we have just gone through, we find

E = Vχ0ρ0 − S ∫ε0 (χ0ρ0 − χρ) dν.    (4)

Multiplying equation (2) by χ0, and subtracting it from (4),

E − Mχ0 = S ∫ε0 (χ − χ0) ρdν    (5)

In this expression M and χ0 are both constant, so that the variation of the right-hand side of the equation is the same as that of the energy E, and expresses that part of the energy which depends on the area of the bounding surface of the liquid. We may call this the surface energy.

The symbol χ expresses the energy of unit of mass of the liquid at a depth ν within the bounding surface. When the liquid is in contact with a rare medium, such as its own vapour or any other gas, χ is greater than χ0, and the surface energy is positive. By the principle of the conservation of energy, any displacement of the liquid by which its energy is diminished will tend to take place of itself. Hence if the energy is the greater, the greater the area of the exposed surface, the liquid will tend to move in such a way as to diminish the area of the exposed surface, or, in other words, the exposed surface will tend to diminish if it can do so consistently with the other conditions. This tendency of the surface to contract itself is called the surface-tension of liquids.

Dupré has described an arrangement by which the surface-tension of a liquid film may be illustrated. A piece of sheet metal is cut out in the form AA (fig. 1). A very fine slip of metal is laid on it in the position BB, and the whole is dipped into a solution of soap, or M. Plateau’s glycerine mixture. When it is taken out the rectangle AACC if filled up by a liquid film. This film, however, tends to contract on itself, and the loose strip of metal BB will, if it is let go, be drawn up towards AA, provided it is sufficiently light and smooth.

Let T be the surface energy per unit of area; then the energy of a surface of area S will be ST. If, in the rectangle AACC, AA = a, and AC = b, its area is S = ab, and its energy Tab. Hence if F is the force by which the slip BB is pulled towards AA,

or the force arising from the surface-tension acting on a length a of the strip is Ta, so that T represents the surface-tension acting transversely on every unit of length of the periphery of the liquid surface. Hence if we write

T = ∫ε0 (χ − χ0) ρ dν,    (7)

we may define T either as the surface-energy per unit of area, or as the surface-tension per unit of contour, for the numerical values of these two quantities are equal.

If the liquid is bounded by a dense substance, whether liquid or solid, the value of χ may be different from its value when the liquid has a free surface. If the liquid is in contact with another liquid, let us distinguish quantities belonging to the two liquids by suffixes. We shall then have

E1 − M1 χ01 = S ∫ε10 (χ1 − χ01) ρ1 dν1,    (8)

E2 − M2 χ02 = S ∫ε20 (χ2 − χ02) ρ2 dν2.    (9)

Adding these expressions, and dividing the second member by S, we obtain for the tension of the surface of contact of the two liquids

T1·2 = ∫ε10 (χ1 − χ01) ρ1 dν1 + ∫ε20 (χ2 − χ02) ρ2 dν2.    (10)

If this quantity is positive, the surface of contact will tend to contract, and the liquids will remain distinct. If, however, it were negative, the displacement of the liquids which tends to enlarge the surface of contact would be aided by the molecular forces, so that the liquids, if not kept separate by gravity, would at length become thoroughly mixed. No instance, however, of a phenomenon of this kind has been discovered, for those liquids which mix of themselves do so by the process of diffusion, which is a molecular motion, and not by the spontaneous puckering and replication of the bounding surface as would be the case if T were negative.

It is probable, however, that there are many cases in which the integral belonging to the less dense fluid is negative. If the denser body be solid we can often demonstrate this; for the liquid tends to spread itself over the surface of the solid, so as to increase the area of the surface of contact, even although in so doing it is obliged to increase the free surface in opposition to the surface-tension. Thus water spreads itself out on a clean surface of glass. This shows that ∫ε0 (χ − χ0)ρdν must be negative for water in contact with glass.

On the Tension of Liquid Films.—The method already given for the investigation of the surface-tension of a liquid, all whose dimensions are sensible, fails in the case of a liquid film such as a soap-bubble. In such a film it is possible that no part of the liquid may be so far from the surface as to have the potential and density corresponding to what we have called the interior of a liquid mass, and measurements of the tension of the film when drawn out to different degrees of thinness may possibly lead to an estimate of the range of the molecular forces, or at least of the depth within a liquid mass, at which its properties become sensibly uniform. We shall therefore indicate a method of investigating the tension of such films.

Let S be the area of the film, M its mass, and E its energy; σ the mass, and e the energy of unit of area; then

M = Sσ,    (11)

E = Se.    (12)

Let us now suppose that by some change in the form of the boundary of the film its area is changed from S to S + dS. If its tension is T the work required to effect this increase of surface will be T dS, and the energy of the film will be increased by this amount. Hence

TdS = dE = Sde + edS.    (13)

But since M is constant,

dM = Sdσ + σdS = 0.    (14)

Eliminating dS from equations (13) and (14), and dividing by S, we find

In this expression σ denotes the mass of unit of area of the film, and e the energy of unit of area.

If we take the axis of z normal to either surface of the film, the radius of curvature of which we suppose to be very great compared with its thickness c, and if ρ is the density, and χ the energy of unit of mass at depth z, then

σ = ∫c0 ρdz,    (16)

and

e = ∫c0 χρdz.    (17)

Both ρ and χ are functions of z, the value of which remains the same when z − c is substituted for z. If the thickness of the film is greater than 2 ε, there will be a stratum of thickness c − 2ε in the middle of the film, within which the values of ρ and χ will be ρ0 and χ0. In the two strata on either side of this the law, according to which ρ and χ depend on the depth, will be the same as in a liquid mass of large dimensions. Hence in this case

σ = (c − 2ε) ρ0 + 2 ∫ε0 ρdν,    (18)

e = (c − 2ε) χ0ρ0 + 2 ∫ε0 χρdν,    (19)

T = 2 ∫ε0 χρ dν − 2χ0 ∫ε0 ρdν = 2 ∫ε0 (χ − χ0) ρdν.    (20)

Hence the tension of a thick film is equal to the sum of the tensions of its two surfaces as already calculated (equation 7). On the hypothesis of uniform density we shall find that this is true for films whose thickness exceeds ε.

The symbol χ is defined as the energy of unit of mass of the substance. A knowledge of the absolute value of this energy is not required, since in every expression in which it occurs it is under the 260 form χ − χ0, that is to say, the difference between the energy in two different states. The only cases, however, in which we have experimental values of this quantity are when the substance is either liquid and surrounded by similar liquid, or gaseous and surrounded by similar gas. It is impossible to make direct measurements of the properties of particles of the substance within the insensible distance ε of the bounding surface.

When a liquid is in thermal and dynamical equilibrium with its vapour, then if ρ′ and χ′ are the values of ρ and χ for the vapour, and ρ0 and χ0 those for the liquid,

χ′ − χ0 = JL − p(1/ρ′ − 1/ρ0),    (21)

where J is the dynamical equivalent of heat, L is the latent heat of unit of mass of the vapour, and p is the pressure. At points in the liquid very near its surface it is probable that χ is greater than χ0, and at points in the gas very near the surface of the liquid it is probable that χ is less than χ′, but this has not as yet been ascertained experimentally. We shall therefore endeavour to apply to this subject the methods used in Thermodynamics, and where these fail us we shall have recourse to the hypotheses of molecular physics.

We have next to determine the value of χ in terms of the action between one particle and another. Let us suppose that the force between two particles m and m’ at the distance f is

F = mm′ (φ(ƒ) + Cƒ-2),    (22)

being reckoned positive when the force is attractive. The actual force between the particles arises in part from their mutual gravitation, which is inversely as the square of the distance. This force is expressed by m m′ Cƒ-2. It is easy to show that a force subject to this law would not account for capillary action. We shall, therefore, in what follows, consider only that part of the force which depends on φ(ƒ), where φ(ƒ) is a function of ƒ which is insensible for all sensible values of ƒ, but which becomes sensible and even enormously great when ƒ is exceedingly small.

If we next introduce a new function of f and write

∫∞ƒ φ(ƒ) dƒ = Π (ƒ),     (23)

then m m′ Π(ƒ) will represent—(I) The work done by the attractive force on the particle m, while it is brought from an infinite distance from m′ to the distance ƒ from m′; or (2) The attraction of a particle m on a narrow straight rod resolved in the direction of the length of the rod, one extremity of the rod being at a distance f from m, and the other at an infinite distance, the mass of unit of length of the rod being m′. The function Π(ƒ) is also insensible for sensible values of ƒ, but for insensible values of ƒ it may become sensible and even very great.

If we next write

∫∞ƒ ƒΠ(ƒ) dƒ = ψ(z),     (24)

then 2πmσψ(z) will represent—(1) The work done by the attractive force while a particle m is brought from an infinite distance to a distance z from an infinitely thin stratum of the substance whose mass per unit of area is σ; (2) The attraction of a particle m placed at a distance z from the plane surface of an infinite solid whose density is σ.

Let us examine the case in which the particle m is placed at a distance z from a curved stratum of the substance, whose principal radii of curvature are R1 and R2. Let P (fig. 2) be the particle and PB a normal to the surface. Let the plane of the paper be a normal section of the surface of the stratum at the point B, making an angle ω with the section whose radius of curvature is R1. Then if O is the centre of curvature in the plane of the paper, and BO = u,

Let

POQ = θ,   PO = r,   PQ = ƒ,   BP = z,

ƒ² = u² + r² − 2ur cos θ.     (26)

The element of the stratum at Q may be expressed by

σu² sin θ dθdω,

or expressing dθ in terms of dƒ by (26),

σur-1ƒ dƒ dθ.

Multiplying this by m and by π(ƒ), we obtain for the work done by the attraction of this element when m is brought from an infinite distance to P1,

mσur-1 ƒΠ(ƒ) dƒdω.

Integrating with respect to ƒ from ƒ = z to ƒ = a, where a is a line very great compared with the extreme range of the molecular force, but very small compared with either of the radii of curvature, we obtain for the work

∫ mσur-1 (ψ(z) − ψ(a)) dω,

and since ψ(a) is an insensible quantity we may omit it. We may also write

ur-1 = 1 + zu-1 + &c.,

since z is very small compared with u, and expressing u in terms of ω by (25), we find

This then expresses the work done by the attractive forces when a particle m is brought from an infinite distance to the point P at a distance z from a stratum whose surface-density is σ, and whose principal radii of curvature are R1 and R2.

To find the work done when m is brought to the point P in the neighbourhood of a solid body, the density of which is a function of the depth ν below the surface, we have only to write instead of σ ρdz, and to integrate

where, in general, we must suppose ρ a function of z. This expression, when integrated, gives (1) the work done on a particle m while it is brought from an infinite distance to the point P, or (2) the attraction on a long slender column normal to the surface and terminating at P, the mass of unit of length of the column being m. In the form of the theory given by Laplace, the density of the liquid was supposed to be uniform. Hence if we write

K = 2π ∫∞0 ψ(z) dz,     H = 2π ∫∞0 zψ(z) dz,

the pressure of a column of the fluid itself terminating at the surface will be

ρ² {K + ½H (1/R1 + 1/R2) },

and the work done by the attractive forces when a particle m is brought to the surface of the fluid from an infinite distance will be

mρ {K + ½H (1/R1 + 1/R2) }.

If we write

∫∞z ψ(z) dz = θ(z),

then 2πmρθ(z) will express the work done by-the attractive forces, while a particle m is brought from an infinite distance to a distance z from the plane surface of a mass of the substance of density ρ and infinitely thick. The function θ(z) is insensible for all sensible values of z. For insensible values it may become sensible, but it must remain finite even when z = 0, in which case θ(0) = K.

If χ′ is the potential energy of unit of mass of the substance in vapour, then at a distance z from the plane surface of the liquid

χ = χ′ − 2πρθ(z).

At the surface

χ = χ′ − 2πρθ(0).

At a distance z within the surface

χ = χ′ − 4πρθ(0) + 2πρθ(z).

If the liquid forms a stratum of thickness c, then

χ = χ′ − 4πρθ(0) + 2πρθ(z) + 2πρθ(z − c).

The surface-density of this stratum is σ = cρ. The energy per unit of area is

e = ∫c0 χρ dz = cρ (χ′ − 4πρθ(0)) + 2πρ² ∫c0 θ(z) dz + 2πρ² ∫c0 θ(z − c) dz.

Since the two sides of the stratum are similar the last two terms are equal, and

e = cρ (χ′ − 4πρθ(0)) + 4πρ² ∫c0 θ(z) dz.

Differentiating with respect to c, we find

Hence the surface-tension

Integrating the first term within brackets by parts, it becomes

Remembering that θ(0) is a finite quantity, and that dθ/dz = − ψ(z), we find

T = 4πρ² ∫c0 zψ(z) dz.     (27)

When c is greater than ε this is equivalent to 2H in the equation of Laplace. Hence the tension is the same for all films thicker than ε, the range of the molecular forces. For thinner films

Hence if ψ(c) is positive, the tension and the thickness will increase together. Now 2πmρψ(c) represents the attraction between a particle m and the plane surface of an infinite mass of the liquid, when the distance of the particle outside the surface is c. Now, the force between the particle and the liquid is certainly, on the whole, attractive; but if between any two small values of c it should be repulsive, then for films whose thickness lies between these values the tension will increase as the thickness diminishes, but for all other cases the tension will diminish as the thickness diminishes.

We have given several examples in which the density is assumed to be uniform, because Poisson has asserted that capillary 261 phenomena would not take place unless the density varied rapidly near the surface. In this assertion we think he was mathematically wrong, though in his own hypothesis that the density does actually vary, he was probably right. In fact, the quantity 4πρ2K, which we may call with van der Waals the molecular pressure, is so great for most liquids (5000 atmospheres for water), that in the parts near the surface, where the molecular pressure varies rapidly, we may expect considerable variation of density, even when we take into account the smallness of the compressibility of liquids.

The pressure at any point of the liquid arises from two causes, the external pressure P to which the liquid is subjected, and the pressure arising from the mutual attraction of its molecules. If we suppose that the number of molecules within the range of the attraction of a given molecule is very large, the part of the pressure arising from attraction will be proportional to the square of the number of molecules in unit of volume, that is, to the square of the density. Hence we may write

p = P + Aρ²,

where A is a constant [equal to Laplace’s intrinsic pressure K. But this equation is applicable only at points in the interior, where ρ is not varying.]

[The intrinsic pressure and the surface-tension of a uniform mass are perhaps more easily found by the following process. The former can be found at once by calculating the mutual attraction of the parts of a large mass which lie on opposite sides of an imaginary plane interface. If the density be σ, the attraction between the whole of one side and a layer upon the other distant z from the plane and of thickness dz is 2 π σ² ψ(z) dz, reckoned per unit of area. The expression for the intrinsic pressure is thus simply

K = 2πσ² ∫∞0 ψ(z) dz.     (28)

In Laplace’s investigation σ is supposed to be unity. We may call the value which (28) then assumes K0, so that as above

K0 = 2π ∫∞0 ψ(z) dz.     (29)

The expression for the superficial tension is most readily found with the aid of the idea of superficial energy, introduced into the subject by Gauss. Since the tension is constant, the work that must be done to extend the surface by one unit of area measures the tension, and the work required for the generation of any surface is the product of the tension and the area. From this consideration we may derive Laplace’s expression, as has been done by Dupre (Théorie mécanique de la chaleur, Paris, 1869), and Kelvin (“Capillary Attraction,” Proc. Roy. Inst., January 1886. Reprinted, Popular Lectures and Addresses, 1889). For imagine a small cavity to be formed in the interior of the mass and to be gradually expanded in such a shape that the walls consist almost entirely of two parallel planes. The distance between the planes is supposed to be very small compared with their ultimate diameters, but at the same time large enough to exceed the range of the attractive forces. The work required to produce this crevasse is twice the product of the tension and the area of one of the faces. If we now suppose the crevasse produced by direct separation of its walls, the work necessary must be the same as before, the initial and final configurations being identical; and we recognize that the tension may be measured by half the work that must be done per unit of area against the mutual attraction in order to separate the two portions which lie upon opposite sides of an ideal plane to a distance from one another which is outside the range of the forces. It only remains to calculate this work.

If σ1, σ2 represent the densities of the two infinite solids, their mutual attraction at distance z is per unit of area

2πσ1σ2 ∫∞0 ψ(z) dz,     (30)

or 2πσ1σ2θ(z), if we write

∫∞0 ψ(z) dz = θ(z)     (31)

The work required to produce the separation in question is thus

2πσ1σ2 ∫∞0 θ(z) dz;     (32)

and for the tension of a liquid of density σ we have

T = πσ² ∫∞0 θ(z) dz.     (33)

The form of this expression may be modified by integration by parts. For

Since θ(0) is finite, proportional to K, the integrated term vanishes at both limits, and we have simply

∫∞0 θ(z) dz = ∫∞0 zψ(z) dz,     (34)

and

T = πσ² ∫∞0 zψ(z) dz.     (35)

In Laplace’s notation the second member of (34), multiplied by 2π, is represented by H.

As Laplace has shown, the values for K and T may also be expressed in terms of the function φ, with which we started. Integrating by parts, we get

∫ψ(z) dz = z ψ(z) + 1⁄3 z3 Π(z) + 1⁄3 ∫z3 φ(z) dz,

∫zψ(z) dz = ½ z2ψ(z) + 1⁄8 z4 Π(z) + 1⁄8 ∫z4 φ(z) dz.

In all cases to which it is necessary to have regard the integrated terms vanish at both limits, and we may write

∫∞0 ψ(z) dz = 1⁄3 ∫∞2 z3 φ(z) dz,   ∫∞0 zψ(z) dz = 1⁄8 ∫∞0 z4 φ(z) dz;     (36)

so that

A few examples of these formulae will promote an intelligent comprehension of the subject. One of the simplest suppositions open to us is that

φ(ƒ) = eβƒ.     (38)

From this we obtain

Π(z) = β-1 e-βz,   ψ(z) = β-3 (βz + 1)e-βz,     (39)

K0 = 4πβ-4,   T0 = 3πβ-5.     (40)

The range of the attractive force is mathematically infinite, but practically of the order β-1, and we see that T is of higher order in this small quantity than K. That K is in all cases of the fourth order and T of the fifth order in the range of the forces is obvious from (37) without integration.

An apparently simple example would be to suppose φ(z) = zn. We get

The intrinsic pressure will thus be infinite whatever n may be. If n + 4 be positive, the attraction of infinitely distant parts contributes to the result; while if n + 4 be negative, the parts in immediate contiguity act with infinite power. For the transition case, discussed by William Sutherland (Phil. Mag. xxiv. p. 113, 1887), of n + 4 = 0, K0 is also infinite. It seems therefore that nothing satisfactory can be arrived at under this head.

As a third example, we will take the law proposed by Young, viz.

and corresponding therewith,

Equations (37) now give

The numerical results differ from those of Young, who finds that “the contractile force is one-third of the whole cohesive force of a stratum of particles, equal in thickness to the interval to which the primitive equable cohesion extends,” viz. T = 1⁄3 aK; whereas according to the above calculation T = 3⁄20 aK. The discrepancy seems to depend upon Young having treated the attractive force as operative in one direction only. For further calculations on Laplace’s principles, see Rayleigh, Phil. Mag., Oct. Dec. 1890, or Scientific Papers, vol. iii. p. 397.]

On Surface-Tension

Definition.—The tension of a liquid surface across any line drawn on the surface is normal to the line, and is the same for all directions of the line, and is measured by the force across an element of the line divided by the length of that element.

Experimental Laws of Surface-Tension.—1. For any given liquid surface, as the surface which separates water from air, or oil from water, the surface-tension is the same at every point of the surface and in every direction. It is also practically independent of the curvature of the surface, although it appears from the mathematical theory that there is a slight increase of tension where the mean curvature of the surface is concave, and a slight diminution where it is convex. The amount of this increase and diminution is too small to be directly measured, though it has a certain theoretical importance in the explanation of the equilibrium of the superficial layer of the liquid where it is inclined to the horizon.

2. The surface-tension diminishes as the temperature rises, and when the temperature reaches that of the critical point at which the distinction between the liquid and its vapour ceases, it has been observed by Andrews that the capillary action also vanishes. The early writers on capillary action supposed that the diminution of capillary action was due simply to the change of density corresponding to the rise of temperature, and, therefore, assuming the surface-tension to vary as the square of the 262 density, they deduced its variations from the observed dilatation of the liquid by heat. This assumption, however, does not appear to be verified by the experiments of Brunner and Wolff on the rise of water in tubes at different temperatures.

3. The tension of the surface separating two liquids which do not mix cannot be deduced by any known method from the tensions of the surfaces of the liquids when separately in contact with air.

When the surface is curved, the effect of the surface-tension is to make the pressure on the concave side exceed the pressure on the convex side by T (1/R1 + 1/R2), where T is the intensity of the surface-tension and R1, R2 are the radii of curvature of any two sections normal to the surface and to each other.

If three fluids which do not mix are in contact with each other, the three surfaces of separation meet in a line, straight or curved. Let O (fig. 3) be a point in this line, and let the plane of the paper be supposed to be normal to the line at the point O. The three angles between the tangent planes to the three surfaces of separation at the point O are completely determined by the tensions of the three surfaces. For if in the triangle abc the side ab is taken so as to represent on a given scale the tension of the surface of contact of the fluids a and b, and if the other sides bc and ca are taken so as to represent on the same scale the tensions of the surfaces between b and c and between c and a respectively, then the condition of equilibrium at O for the corresponding tensions R, P and Q is that the angle ROP shall be the supplement of abc, POQ of bca, and, therefore, QOR of cab. Thus the angles at which the surfaces of separation meet are the same at all parts of the line of concourse of the three fluids. When three films of the same liquid meet, their tensions are equal, and, therefore, they make angles of 120° with each other. The froth of soap-suds or beaten-up eggs consists of a multitude of small films which meet each other at angles of 120°.

If four fluids, a, b, c, d, meet in a point O, and if a tetrahedron ABCD is formed so that its edge AB represents the tension of the surface of contact of the liquids a and b, BC that of b and c, and so on; then if we place this tetrahedron so that the face ABC is normal to the tangent at O to the line of concourse of the fluids abc, and turn it so that the edge AB is normal to the tangent plane at O to the surface of contact of the fluids a and b, then the other three faces of the tetrahedron will be normal to the tangents at O to the other three lines of concourse of the liquids, and the other five edges of the tetrahedron will be normal to the tangent planes at O to the other five surfaces of contact.

If six films of the same liquid meet in a point the corresponding tetrahedron is a regular tetrahedron, and each film, where it meets the others, has an angle whose cosine is −1⁄3. Hence if we take two nets of wire with hexagonal meshes, and place one on the other so that the point of concourse of three hexagons of one net coincides with the middle of a hexagon of the other, and if we then, after dipping them in Plateau’s liquid, place them horizontally, and gently raise the upper one, we shall develop a system of plane laminae arranged as the walls and floors of the cells are arranged in a honeycomb. We must not, however, raise the upper net too much, or the system of films will become unstable.

When a drop of one liquid, B, is placed on the surface of another, A, the phenomena which take place depend on the relative magnitude of the three surface-tensions corresponding to the surface between A and air, between B and air, and between A and B. If no one of these tensions is greater than the sum of the other two, the drop will assume the form of a lens, the angles which the upper and lower surfaces of the lens make with the free surface of A and with each other being equal to the external angles of the triangle of forces. Such lenses are often seen formed by drops of fat floating on the surface of hot water, soup or gravy. But when the surface-tension of A exceeds the sum of the tensions of the surfaces of contact of B with air and with A, it is impossible to construct the triangle of forces; so that equilibrium becomes impossible. The edge of the drop is drawn out by the surface-tension of A with a force greater than the sum of the tensions of the two surfaces of the drop. The drop, therefore, spreads itself out, with great velocity, over the surface of A till it covers an enormous area, and is reduced to such extreme tenuity that it is not probable that it retains the same properties of surface-tension which it has in a large mass. Thus a drop of train oil will spread itself over the surface of the sea till it shows the colours of thin plates. These rapidly descend in Newton’s scale and at last disappear, showing that the thickness of the film is less than the tenth part of the length of a wave of light. But even when thus attenuated, the film may be proved to be present, since the surface-tension of the liquid is considerably less than that of pure water. This may be shown by placing another drop of oil on the surface. This drop will not spread out like the first drop, but will take the form of a flat lens with a distinct circular edge, showing that the surface-tension of what is still apparently pure water is now less than the sum of the tensions of the surfaces separating oil from air and water.

The spreading of drops on the surface of a liquid has formed the subject of a very extensive series of experiments by Charles Tomlinson; van der Mensbrugghe has also written a very complete memoir on this subject (Sur la tension superficielle des liquides, Bruxelles, 1873).

When a solid body is in contact with two fluids, the surface of the solid cannot alter its form, but the angle at which the surface of contact of the two fluids meets the surface of the solid depends on the values of the three surface-tensions. If a and b are the two fluids and c the solid then the equilibrium of the tensions at the point O depends only on that of thin components parallel to the surface, because the surface-tensions normal to the surface are balanced by the resistance of the solid. Hence if the angle ROQ (fig. 4) at which the surface of contact OP meets the solid is denoted by α,

Tbc − Tca − Tab cos α = 0,

Whence

cos α = (Tbc − Tca) / Tab.

As an experiment on the angle of contact only gives us the difference of the surface-tensions at the solid surface, we cannot determine their actual value. It is theoretically probable that they are often negative, and may be called surface-pressures.

The constancy of the angle of contact between the surface of a fluid and a solid was first pointed out by Dr Young, who states that the angle of contact between mercury and glass is about 140°. Quincke makes it 128° 52′.

If the tension of the surface between the solid and one of the fluids exceeds the sum of the other two tensions, the point of contact will not be in equilibrium, but will be dragged towards the side on which the tension is greatest. If the quantity of the first fluid is small it will stand in a drop on the surface of the solid without wetting it. If the quantity of the second fluid is small it will spread itself over the surface and wet the solid. The angle of contact of the first fluid is 180° and that of the second is zero.

If a drop of alcohol be made to touch one side of a drop of oil on a glass plate, the alcohol will appear to chase the oil over the plate, and if a drop of water and a drop of bisulphide of carbon be placed in contact in a horizontal capillary tube, the bisulphide of carbon will chase the water along the tube. In both cases the liquids move in the direction in which the surface-pressure at the solid is least.

[In order to express the dependence of the tension at the interface of two bodies in terms of the forces exercised by the bodies upon themselves and upon one another, we cannot do better than follow the method of Dupré. If T12 denote the interfacial tension, the energy corresponding to unit of area of the interface 263 is also T12, as we see by considering the introduction (through a fine tube) of one body into the interior of the other. A comparison with another method of generating the interface, similar to that previously employed when but one body was in question, will now allow us to evaluate T12.

The work required to cleave asunder the parts of the first fluid which lie on the two sides of an ideal plane passing through the interior, is per unit of area 2T1, and the free surface produced is two units in area. So for the second fluid the corresponding work is 2T2. This having been effected, let us now suppose that each of the units of area of free surface of fluid (1) is allowed to approach normally a unit area of (2) until contact is established. In this process work is gained which we may denote by 4T′12, 2T′12 for each pair. On the whole, then, the work expended in producing two units of interface is 2T1 + 2T2 − 4T′12, and this, as we have seen, may be equated to 2T12. Hence

T12 = T1 + T2 − 2T′12     (47)

If the two bodies are similar,

T1 = T2 = T′12;

and T12 = 0, as it should do.

Laplace does not treat systematically the question of interfacial tension, but he gives incidentally in terms of his quantity H a relation analogous to (47).

If 2T′12 > T1 + T2, T12 would be negative, so that the interface would of itself tend to increase. In this case the fluids must mix. Conversely, if two fluids mix, it would seem that T′12 must exceed the mean of T1 and T2; otherwise work would have to be expended to effect a close alternate stratification of the two bodies, such as we may suppose to constitute a first step in the process of mixture (Dupré, Théorie mécanique de la chaleur, p. 372; Kelvin, Popular Lectures, p. 53).

The value of T′12 has already been calculated (32). We may write

T′12 = πσ1σ2 ∫∞0 θ(z) dz = 1⁄8 πσ1σ2 ∫∞0 z4φ(z) dz;     (48)

and in general the functions θ, or φ, must be regarded as capable of assuming different forms. Under these circumstances there is no limitation upon the values of the interfacial tensions for three fluids, which we may denote by T12, T23, T31. If the three fluids can remain in contact with one another, the sum of any two of the quantities must exceed the third, and by Neumann’s rule the directions of the interfaces at the common edge must be parallel to the sides of a triangle, taken proportional to T12, T23, T31. If the above-mentioned condition be not satisfied, the triangle is imaginary, and the three fluids cannot rest in contact, the two weaker tensions, even if acting in full concert, being incapable of balancing the strongest. For instance, if T31 > T12 + T23, the second fluid spreads itself indefinitely upon the interface of the first and third fluids.

The experimenters who have dealt with this question, C.G.M. Marangoni, van der Mensbrugghe, Quincke, have all arrived at results inconsistent with the reality of Neumann’s triangle. Thus Marangoni says (Pogg. Annalen, cxliii. p. 348, 1871):—“Die gemeinschaftliche Oberfläche zweier Flüssigkeiten hat eine geringere Oberflächenspannung als die Differenz der Oberflächenspannung der Flüssigkeiten selbst (mit Ausnahme des Quecksilbers).” Three pure bodies (of which one may be air) cannot accordingly remain in contact. If a drop of oil stands in lenticular form upon a surface of water, it is because the water-surface is already contaminated with a greasy film.

On the theoretical side the question is open until we introduce some limitation upon the generality of the functions. By far the simplest supposition open to us is that the functions are the same in all cases, the attractions differing merely by coefficients analogous to densities in the theory of gravitation. This hypothesis was suggested by Laplace, and may conveniently be named after him. It was also tacitly adopted by Young, in connexion with the still more special hypothesis which Young probably had in view, namely that the force in each case was constant within a limited range, the same in all cases, and vanished outside that range.

As an immediate consequence of this hypothesis we have from (28)

K = K0σ²,     (49)

T = T0σ²,     (50)

where K0, T0 are the same for all bodies.

But the most interesting results are those which Young (Works, vol. i. p. 463) deduced relative to the interfacial tensions of three bodies. By (37), (48),

T′12 = σ1σ2T0;     (51)

so that by (47), (50),

T12 = (σ1 − σ2)² T0     (52)

According to (52), the interfacial tension between any two bodies is proportional to the square of the difference of their densities. The densities σ1, σ2, σ3 being in descending order of magnitude, we may write

T31 = (σ1 − σ2 + σ2 − σ3)² T0 = T12 + T23 + 2(σ1 − σ2) (σ2 − σ3)T0;

so that T31 necessarily exceeds the sum of the other two interfacial tensions. We are thus led to the important conclusion that according to this hypothesis Neumann’s triangle is necessarily imaginary, that one of three fluids will always spread upon the interface of the other two.

Another point of importance may be easily illustrated by this theory, viz. the dependency of capillarity upon abruptness of transition. “The reason why the capillary force should disappear when the transition between two liquids is sufficiently gradual will now be evident. Suppose that the transition from 0 to σ is made in two equal steps, the thickness of the intermediate layer of density ½σ being large compared to the range of the molecular forces, but small in comparison with the radius of curvature. At each step the difference of capillary pressure is only one-quarter of that due to the sudden transition from 0 to σ, and thus altogether half the effect is lost by the interposition of the layer. If there were three equal steps, the effect would be reduced to one-third, and so on. When the number of steps is infinite, the capillary pressure disappears altogether.” (“Laplace’s Theory of Capillarity,” Rayleigh, Phil. Mag., 1883, p. 315.)

According to Laplace’s hypothesis the whole energy of any number of contiguous strata of liquids is least when they are arranged in order of density, so that this is the disposition favoured by the attractive forces. The problem is to make the sum of the interfacial tensions a minimum, each tension being proportional to the square of the difference of densities of the two contiguous liquids in question. If the order of stratification differ from that of densities, we can show that each step of approximation to this order lowers the sum of tensions. To this end consider the effect of the abolition of a stratum σn+1, contiguous to σn and σn+2. Before the change we have (σn − σn+1)² + (σn+1 − σn+2)², and afterwards (σn − σn+2)². The second minus the first, or the increase in the sum of tensions, is thus

2(σn − σn+1) (σn+1 − σn+2).

Hence, if σn+1 be intermediate in magnitude between σn and σn+2, the sum of tensions is increased by the abolition of the stratum; but, if σn+1 be not intermediate, the sum is decreased. We see, then, that the removal of a stratum from between neighbours where it is out of order and its introduction between neighbours where it will be in order is doubly favourable to the reduction of the sum of tensions; and since by a succession of such steps we may arrive at the order of magnitude throughout, we conclude that this is the disposition of minimum tensions and energy.

So far the results of Laplace’s hypothesis are in marked accordance with experiment; but if we follow it out further, discordances begin to manifest themselves. According to (52)

√T31 = √T12 + √T23,     (53)

a relation not verified by experiment. What is more, (52) shows that according to the hypothesis T12 is necessarily positive; 264 so that, if the preceding argument be correct, no such thing as mixture of two liquids could ever take place.

There are two apparent exceptions to Marangoni’s rule which call for a word of explanation. According to the rule, water, which has the lower surface-tension, should spread upon the surface of mercury; whereas the universal experience of the laboratory is that drops of water standing upon mercury retain their compact form without the least tendency to spread. To Quincke belongs the credit of dissipating the apparent exception. He found that mercury specially prepared behaves quite differently from ordinary mercury, and that a drop of water deposited thereon spreads over the entire surface. The ordinary behaviour is evidently the result of a film of grease, which adheres with great obstinacy.

The process described by Quincke is somewhat elaborate; but there is little difficulty in repeating the experiment if the mistake be avoided of using a free surface already contaminated, as almost inevitably happens when the mercury is poured from an ordinary bottle. The mercury should be drawn from underneath, for which purpose an arrangement similar to a chemical wash bottle is suitable, and it may be poured into watch-glasses, previously dipped into strong sulphuric acid, rinsed in distilled water, and dried over a Bunsen flame. When the glasses are cool, they may be charged with mercury, of which the first part is rejected. Operating in this way there is no difficulty in obtaining surfaces upon which a drop of water spreads, although from causes that cannot always be traced, a certain proportion of failures is met with. As might be expected, the grease which produces these effects is largely volatile. In many cases a very moderate preliminary warming of the watch-glasses makes all the difference in the behaviour of the drop.

The behaviour of a drop of carbon bisulphide placed upon clean water is also, at first sight, an exception to Marangoni’s rule. So far from spreading over the surface, as according to its lower surface-tension it ought to do, it remains suspended in the form of a lens. Any dust that may be lying upon the surface is not driven away to the edge of the drop, as would happen in the case of oil. A simple modification of the experiment suffices, however, to clear up the difficulty. If after the deposition of the drop, a little lycopodium be scattered over the surface, it is seen that a circular space surrounding the drop, of about the size of a shilling, remains bare, and this, however often the dusting be repeated, so long as any of the carbon bisulphide remains. The interpretation can hardly be doubtful. The carbon bisulphide is really spreading all the while, but on account of its volatility is unable to reach any considerable distance. Immediately surrounding the drop there is a film moving outwards at a high speed, and this carries away almost instantaneously any dust that may fall upon it. The phenomenon above described requires that the water-surface be clean. If a very little grease be present, there is no outward flow and dust remains undisturbed in the immediate neighbourhood of the drop.]

On the Rise of a Liquid in a Tube.—Let a tube (fig. 6) whose internal radius is r, made of a solid substance c, be dipped into a liquid a. Let us suppose that the angle of contact for this liquid with the solid c is an acute angle. This implies that the tension of the free surface of the solid c is greater than that of the surface of contact of the solid with the liquid a. Now consider the tension of the free surface of the liquid a. All round its edge there is a tension T acting at an angle a with the vertical. The circumference of the edge is 2πr, so that the resultant of this tension is a force 2πrT cos α acting vertically upwards on the liquid. Hence the liquid will rise in the tube till the weight of the vertical column between the free surface and the level of the liquid in the vessel balances the resultant of the surface-tension. The upper surface of this column is not level, so that the height of the column cannot be directly measured, but let us assume that h is the mean height of the column, that is to say, the height of a column of equal weight, but with a flat top. Then if r is the radius of the tube at the top of the column, the volume of the suspended column is πr²h, and its weight is πρgr²h, when ρ is its density and g the intensity of gravity. Equating this force with the resultant of the tension

πρgr²h = 2πrT cos α,

or

h = 2T cos α/ρgr.

Hence the mean height to which the fluid rises is inversely as the radius of the tube. For water in a clean glass tube the angle of contact is zero, and

h = 2T / ρgr.

For mercury in a glass tube the angle of contact is 128° 52′, the cosine of which is negative. Hence when a glass tube is dipped into a vessel of mercury, the mercury within the tube stands at a lower level than outside it.

Rise of a Liquid between Two Plates.—When two parallel plates are placed vertically in a liquid the liquid rises between them. If we now suppose fig. 6 to represent a vertical section perpendicular to the plates, we may calculate the rise of the liquid. Let l be the breadth of the plates measured perpendicularly to the plane of the paper, then the length of the line which bounds the wet and the dry parts of the plates inside is l for each surface, and on this the tension T acts at an angle α to the vertical. Hence the resultant of the surface-tension is 2lT cos α. If the distance between the inner surfaces of the plates is a, and if the mean height of the film of fluid which rises between them is h, the weight of fluid raised is ρghla. Equating the forces—

ρghla = 2lT cos α,

whence

h = 2T cos α/ρga.

This expression is the same as that for the rise of a liquid in a tube, except that instead of r, the radius of the tube, we have a the distance of the plates.

Form of the Capillary Surface.—The form of the surface of a liquid acted on by gravity is easily determined if we assume that near the part considered the line of contact of the surface of the liquid with that of the solid bounding it is straight and horizontal, as it is when the solids which constrain the liquid are bounded by surfaces formed by horizontal and parallel generating lines. This will be the case, for instance, near a flat plate dipped into the liquid. If we suppose these generating lines to be normal to the plane of the paper, then all sections of the solids parallel to this plane will be equal and similar to each other, and the section of the surface of the liquid will be of the same form for all such sections.

Let us consider the portion of the liquid between two parallel sections distant one unit of length. Let P1, P2 (fig. 7) be two points of the surface; θ1, θ2 the inclination of the surface to the horizon at P1 and P2; y1, y2 the heights of P1 and P2 above the level of the liquid at a distance from all solid bodies. The pressure at any point of the liquid which is above this level is negative unless another fluid as, for instance, the air, presses on the upper surface, but it is only the difference of pressures with which we have to do, because two equal pressures on opposite sides of the surface produce no effect.

We may, therefore, write for the pressure at a height y

p = −ρgy,

265

where ρ is the density of the liquid, or if there are two fluids the excess of the density of the lower fluid over that of the upper one.

The forces acting on the portion of liquid P1P2A2A1 are—first, the horizontal pressures, −½ρgy1² and ½ρgy2²; second, the surface-tension T acting at P1 and P2 in directions inclined θ1 and θ2 to the horizon. Resolving horizontally we find—

T(cosθ2 − cosθ1) + ½gρ(y2² − y1²) = 0,

whence

or if we suppose P1 fixed and P2 variable, we may write

cosθ = constant − ½gρy² / T.

This equation gives a relation between the inclination of the curve to the horizon and the height above the level of the liquid.

Resolving vertically we find that the weight of the liquid raised above the level must be equal to T(sinθ2 − sinθ1), and this is therefore equal to the area P1P2A2A1 multiplied by gρ. The form of the capillary surface is identical with that of the “elastic curve,” or the curve formed by a uniform spring originally straight, when its ends are acted on by equal and opposite forces applied either to the ends themselves or to solid pieces attached to them. Drawings of the different forms of the curve may be found in Thomson and Tait’s Natural Philosophy, vol. i. p. 455.

We shall next consider the rise of a liquid between two plates of different materials for which the angles of contact are α1 and α2, the distance between the plates being a, a small quantity. Since the plates are very near one another we may use the following equation of the surface as an approximation:—

y = h1 + Ax + Bx²,   h2 = h1 + Aa + Ba²,

whence

cot α1 = −A,   cot α2 = A + 2Ba

T(cos α1 + cos α2) = ρga(h1 + ½Aa + 1⁄3Ba²),

whence we obtain

Let X be the force which must be applied in a horizontal direction to either plate to keep it from approaching the other, then the forces acting on the first plate are T + X in the negative direction, and T sin α1 + ½gρh1² in the positive direction. Hence

X = ½gρh1² − T(1 − sin α1).

For the second plate

X = ½gρh2² − T(1 − sin α2).

Hence

X = ¼gρ(h1² + h2²) − T{1 − ½(sin α1 + sin α2)},

or, substituting the values of h1 and h2,

the remaining terms being negligible when a is small. The force, therefore, with which the two plates are drawn together consists first of a positive part, or in other words an attraction, varying inversely as the square of the distance, and second, of a negative part of repulsion independent of the distance. Hence in all cases except that in which the angles α1 and α2 are supplementary to each other, the force is attractive when α is small enough, but when cos α1 and cos α2 are of different signs, as when the liquid is raised by one plate, and depressed by the other, the first term may be so small that the repulsion indicated by the second term comes into play. The fact that a pair of plates which repel one another at a certain distance may attract one another at a smaller distance was deduced by Laplace from theory, and verified by the observations of the abbé Haüy.

A Drop between Two Plates.—If a small quantity of a liquid which wets glass be introduced between two glass plates slightly inclined to each other, it will run towards that part where the glass plates are nearest together. When the liquid is in equilibrium it forms a thin film, the outer edge of which is all of the same thickness. If d is the distance between the plates at the edge of the film and Π the atmospheric pressure, the pressure of the liquid in the film is Π − (2T cos α)/d, and if A is the area of the film between the plates and B its circumference, the plates will be pressed together with a force

and this, whether the atmosphere exerts any pressure or not. The force thus produced by the introduction of a drop of water between two plates is enormous, and is often sufficient to press certain parts of the plates together so powerfully as to bruise them or break them. When two blocks of ice are placed loosely together so that the superfluous water which melts from them may drain away, the remaining water draws the blocks together with a force sufficient to cause the blocks to adhere by the process called Regelation.

[An effect of an opposite character may be observed when the fluid is mercury in place of water. When two pieces of flat glass are pressed together under mercury with moderate force they cohere, the mercury leaving the narrow crevasses, even although the alternative is a vacuum. The course of events is more easily followed if one of the pieces of glass constitutes the bottom, or a side, of the vessel containing the mercury.]

In many experiments bodies are floated on the surface of water in order that they may be free to move under the action of slight horizontal forces. Thus Sir Isaac Newton placed a magnet in a floating vessel and a piece of iron in another in order to observe their mutual action, and A.M. Ampère floated a voltaic battery with a coil of wire in its circuit in order to observe the effects of the earth’s magnetism on the electric circuit. When such floating bodies come near the edge of the vessel they are drawn up to it, and are apt to stick fast to it. There are two ways of avoiding this inconvenience. One is to grease the float round its water-line so that the water is depressed round it. This, however, often produces a worse disturbing effect, because a thin film of grease spreads over the water and increases its surface-viscosity. The other method is to fill the vessel with water till the level of the water stands a little higher than the rim of the vessel. The float will then be repelled from the edge of the vessel. Such floats, however, should always be made so that the section taken at the level of the water is as small as possible.

[The Size of Drops.—The relation between the diameter of a tube and the weight of the drop which it delivers appears to have been first investigated by Thomas Tate (Phil. Mag. vol. xxvii. p. 176, 1864), whose experiments led him to the conclusion that “other things being the same, the weight of a drop of liquid is proportional to the diameter of the tube in which it is formed.” Sufficient time must of course be allowed for the formation of the drops; otherwise no simple results can be expected. In Tate’s experiments the period was never less than 40 seconds.

The magnitude of a drop delivered from a tube, even when the formation up to the phase of instability is infinitely slow, cannot be calculated a priori. The weight is sometimes equated to the product of the capillary tension (T) and the circumference of the tube (2πa), but with little justification. Even if the tension at the circumference of the tube acted vertically, and the whole of the liquid below this level passed into the drop, the calculation would still be vitiated by the assumption that the internal pressure at the level in question is atmospheric. It would be necessary to consider the curvatures of the fluid surface at the edge of attachment. If the surface could be treated as a cylindrical prolongation of the tube (radius a), the pressure would be T/a, and the resulting force acting downwards upon the drop would amount to one-half (πaT) of the direct upward pull of the tension along the circumference. At this 266 rate the drop would be but one-half of that above reckoned. But the truth is that a complete solution of the statical problem for all forms up to that at which instability sets in, would not suffice for the present purpose. The detachment of the drop is a dynamical effect, and it is influenced by collateral circumstances. For example, the bore of the tube is no longer a matter of indifference, even though the attachment of the drop occurs entirely at the outer edge. It appears that when the external diameter exceeds a certain value, the weight of a drop of water is sensibly different in the two extreme cases of a very small and of a very large bore.

But although a complete solution of the dynamical problem is impracticable, much interesting information may be obtained from the principle of dynamical similarity. The argument has already been applied by Dupré (Théorie mécanique de la chaleur, Paris, 1869, p. 328), but his presentation of it is rather obscure. We will assume that when, as in most cases, viscosity may be neglected, the mass (M) of a drop depends only upon the density (σ), the capillary tension (T), the acceleration of gravity (g), and the linear dimension of the tube (a). In order to justify this assumption, the formation of the drop must be sufficiently slow, and certain restrictions must be imposed upon the shape of the tube. For example, in the case of water delivered from a glass tube, which is cut off square and held vertically, a will be the external radius; and it will be necessary to suppose that the ratio of the internal radius to a is constant, the cases of a ratio infinitely small, or infinitely near unity, being included. But if the fluid be mercury, the flat end of the tube remains unwetted, and the formation of the drop depends upon the internal diameter only.

The “dimensions” of the quantities on which M depends are:—

of which M, a mass, is to be expressed as a function. If we assume

M ∝ Tx·gy·σz·au,

we have, considering in turn length, time and mass,

y − 3z + u = 0,   2x + 2y = 0,   x + z = 1;

so that

y = −x,   z = 1 − x,   u = 3 − 2x.

Accordingly

Since x is undetermined, all that we can conclude is that M is of the form

where F denotes an arbitrary function.

Dynamical similarity requires that T/gσa² be constant; or, if g be supposed to be so, that a² varies as T/σ. If this condition be satisfied, the mass (or weight) of the drop is proportional to T and to a.

If Tate’s law be true, that ceteris paribus M varies as a, it follows from (1) that F is constant. For all fluids and for all similar tubes similarly wetted, the weight of a drop would then be proportional not only to the diameter of the tube, but also to the superficial tension, and it would be independent of the density.

Careful observations with special precautions to ensure the cleanliness of the water have shown that over a considerable range, the departure from Tate’s law is not great. The results give material for the determination of the function F in (1).

In the preceding table, applicable to thin-walled tubes, the first column gives the values of T/gσa², and the second column those of gM/Ta, all the quantities concerned being in C.G.S. measure, or other consistent system. From this the weight of a drop of any liquid of which the density and surface tension are known, can be calculated. For many purposes it may suffice to treat F as a constant, say 3.8. The formula for the weight of a drop is then simply

Mg = 3.8Ta,     (2)

in which 3.8 replaces the 2π of the faulty theory alluded to earlier (see Rayleigh, Phil. Mag., Oct. 1899).]

Phenomena arising from the Variation of the Surface-tension.—Pure water has a higher surface-tension than that of any other substance liquid at ordinary temperatures except mercury. Hence any other liquid if mixed with water diminishes its surface-tension. For example, if a drop of alcohol be placed on the surface of water, the surface-tension will be diminished from 80, the value for pure water, to 25, the value for pure alcohol. The surface of the liquid will therefore no longer be in equilibrium, and a current will be formed at and near the surface from the alcohol to the surrounding water, and this current will go on as long as there is more alcohol at one part of the surface than at another. If the vessel is deep, these currents will be balanced by counter currents below them, but if the depth of the water is only two or three millimetres, the surface-current will sweep away the whole of the water, leaving a dry spot where the alcohol was dropped in. This phenomenon was first described and explained by James Thomson, who also explained a phenomenon, the converse of this, called the “tears of strong wine.”

If a wine-glass be half-filled with port wine the liquid rises a little up the side of the glass as other liquids do. The wine, however, contains alcohol and water, both of which evaporate, but the alcohol faster than the water, so that the superficial layer becomes more watery. In the middle of the vessel the superficial layer recovers its strength by diffusion from below, but the film adhering to the side of the glass becomes more watery, and therefore has a higher surface-tension than the surface of the stronger wine. It therefore creeps up the side of the glass dragging the strong wine after it, and this goes on till the quantity of fluid dragged up collects into a drop and runs down the side of the glass.

The motion of small pieces of camphor floating on water arises from the gradual solution of the camphor. If this takes place more rapidly on one side of the piece of camphor than on the other side, the surface-tension becomes weaker where there is most camphor in solution, and the lump, being pulled unequally by the surface-tensions, moves off in the direction of the strongest tension, namely, towards the side on which least camphor is dissolved.

If a drop of ether is held near the surface of water the vapour of ether condenses on the surface of the water, and surface-currents are formed flowing in every direction away from under the drop of ether.

If we place a small floating body in a shallow vessel of water and wet one side of it with alcohol or ether, it will move off with great velocity and skim about on the surface of the water, the part wet with alcohol being always the stern.

The surface-tension of mercury is greatly altered by slight changes in the state of the surface. The surface-tension of pure mercury is so great that it is very difficult to keep it clean, for every kind of oil or grease spreads over it at once.

But the most remarkable effects of change of surface-tension are those produced by what is called the electric polarization of the surface. The tension of the surface of contact of mercury and dilute sulphuric acid depends on the electromotive force acting between the mercury and the acid. If the electromotive force is from the acid to the mercury the surface-tension increases; if it is from the mercury to the acid, it diminishes. Faraday observed that a large drop of mercury, resting on the flat bottom of a vessel containing dilute acid, changes its form in a remarkable way when connected with one of the electrodes of a battery, the other electrode being placed in the acid. When the mercury 267 is made positive it becomes dull and spreads itself out; when it is made negative it gathers itself together and becomes bright again. G. Lippmann, who has made a careful investigation of the subject, finds that exceedingly small variations of the electromotive force produce sensible changes in the surface-tension. The effect of one of a Daniell’s cell is to increase the tension from 30.4 to 40.6. He has constructed a capillary electrometer by which differences of electric potential less than 0.01 of that of a Daniell’s cell can be detected by the difference of the pressure required to force the mercury to a given point of a fine capillary tube. He has also constructed an apparatus in which this variation in the surface-tension is made to do work and drive a machine. He has also found that this action is reversible, for when the area of the surface of contact of the acid and mercury is made to increase, an electric current passes from the mercury to the acid, the amount of electricity which passes while the surface increases by one square centimetre being sufficient to decompose .000013 gramme of water.

[The movements of camphor scrapings referred to above afford a useful test of the condition of a water surface. If the contamination exceed a certain limit, the scrapings remain quite dead. In a striking form of the experiment, the water is contained, to the depth of perhaps one inch, in a large flat dish, and the operative part of the surface is limited by a flexible hoop of thin sheet brass lying in the dish and rising above the water-level. If the hoop enclose an area of (say) one-third of the maximum, and if the water be clean, camphor fragments floating on the interior enter with vigorous movements. A touch of the finger will then often reduce them to quiet; but if the hoop be expanded, the included grease is so far attenuated as to lose its effect. Another method of removing grease is to immerse and remove strips of paper by which the surface available for the contamination is in effect increased.

The thickness of the film of oil adequate to check the camphor movements can be determined with fair accuracy by depositing a weighed amount of oil (such as .8 mg.) upon the surface of water in a large bath. Calculated as if the density were the same as in a normal state, the thickness of the film is found to be about two millionths of a millimetre.

Small as is the above amount of oil, the camphor test is a comparatively coarse one. Conditions of a contaminated surface may easily be distinguished, upon all of which camphor fragments spin vigorously. Thus, a shallow tin vessel, such as the lid of a biscuit box, may be levelled and filled with tap-water through a rubber hose. Upon the surface of the water a little sulphur is dusted. An application of the finger for 20 or 30 seconds to the under surface of the vessel will then generate enough heat to lower appreciably the surface-tension, as is evidenced by the opening out of the dust and the formation of a bare spot perhaps 1½ in. in diameter. When, however, the surface is but very slightly greased, a spot can no longer be cleared by the warmth of the finger, or even of a spirit lamp, held underneath. And yet the greasing may be so slight that camphor fragments move with apparently unabated vigour.

The varying degrees of contamination to which a water surface is subject are the cause of many curious phenomena. Among these is the superficial viscosity of Plateau. In his experiments a long compass needle is mounted so as to swing in the surface of the liquid under investigation. The cases of ordinary clean water and alcohol are strongly contrasted, the motion of the needle upon the former being comparatively sluggish. Moreover, a different behaviour is observed when the surfaces are slightly dusted over. In the case of water the whole of the surface in front of the needle moves with it, while on the other hand the dust floating on alcohol is scarcely disturbed until the needle actually strikes it. Plateau attributed these differences to a special quality of the liquids, named by him “superficial viscosity.” It has been proved, however, that the question is one of contamination, and that a water surface may be prepared so as to behave in the same manner as alcohol.

Another consequence of the tendency of a moderate contamination to distribute itself uniformly is the calming effect of oil, investigated by B. Franklin. On pure water the propagation of waves would be attended by temporary extensions and contractions of the surface, but these, as was shown by O. Reynolds, are resisted when the surface is contaminated.

Indeed the possibility of the continued existence of films, such as constitute foam, depends upon the properties now under consideration. If, as is sometimes stated, the tension of a vertical film were absolutely the same throughout, the middle parts would of necessity fall with the acceleration of gravity. In reality, the tension adjusts itself automatically to the weight to be supported at the various levels.

Although throughout a certain range the surface-tension varies rapidly with the degree of contamination, it is remarkable that, as was first fully indicated by Miss Pockels, the earlier stages of contamination have little or no effect upon surface-tension. Lord Rayleigh has shown that the fall of surface-tension begins when the quantity of oil is about the half of that required to stop the camphor movements, and he suggests that this stage may correspond with a complete coating of the surface with a single layer of molecules.]

On the Forms of Liquid Films which are Figures of Revolution.— A soap bubble is simply a small quantity of soap-suds spread out so as to expose a large surface to the air. The bubble, in fact, has two surfaces, an outer and an inner Spherical soap-bubble. surface, both exposed to air. It has, therefore, a certain amount of surface-energy depending on the area of these two surfaces. Since in the case of thin films the outer and inner surfaces are approximately equal, we shall consider the area of the film as representing either of them, and shall use the symbol T to denote the energy of unit of area of the film, both surfaces being taken together. If T′ is the energy of a single surface of the liquid, T the energy of the film is 2T′. When by means of a tube we blow air into the inside of the bubble we increase its volume and therefore its surface, and at the same time we do work in forcing air into it, and thus increase the energy of the bubble.

That the bubble has energy may be shown by leaving the end of the tube open. The bubble will contract, forcing the air out, and the current of air blown through the tube may be made to deflect the flame of a candle. If the bubble is in the form of a sphere of radius r this material surface will have an area

S = 4πr².     (1)

If T be the energy corresponding to unit of area of the film the surface-energy of the whole bubble will be

ST = 4πr²T.     (2)

The increment of this energy corresponding to an increase of the radius from r to r + dr is therefore

TdS = 8πTdr.     (3)

Now this increase of energy was obtained by forcing in air at a pressure greater than the atmospheric pressure, and thus increasing the volume of the bubble.

Let Π be the atmospheric pressure and Π + p the pressure of the air within the bubble. The volume of the sphere is

V = 4⁄3 πr3,     (4)

and the increment of volume is

dV = 4πr²dr.     (5)

Now if we suppose a quantity of air already at the pressure Π + p, the work done in forcing it into the bubble pdV. Hence the equation of work and energy is

p dV = Tds     (6)

or

4πpr²dr = 8πrdrT     (7)

or

p = 2T/r.     (8)

This, therefore, is the excess of the pressure of the air within the bubble over that of the external air, and it is due to the action of the inner and outer surfaces of the bubble. We may conceive this pressure to arise from the tendency which the bubble has to contract, or in other words from the surface-tension of the bubble.

If to increase the area of the surface requires the expenditure 268 of work, the surface must resist extension, and if the bubble in contracting can do work, the surface must tend to contract. The surface must therefore act like a sheet of india-rubber when extended both in length and breadth, that is, it must exert surface-tension. The tension of the sheet of india-rubber, however, depends on the extent to which it is stretched, and may be different in different directions, whereas the tension of the surface of a liquid remains the same however much the film is extended, and the tension at any point is the same in all directions.

The intensity of this surface-tension is measured by the stress which it exerts across a line of unit length. Let us measure it in the case of the spherical soap-bubble by considering the stress exerted by one hemisphere of the bubble on the other, across the circumference of a great circle. This stress is balanced by the pressure p acting over the area of the same great circle: it is therefore equal to πr²p. To determine the intensity of the surface-tension we have to divide this quantity by the length of the line across which it acts, which is in this case the circumference of a great circle 2πr. Dividing πr²p by this length we obtain ½pr as the value of the intensity of the surface-tension, and it is plain from equation 8 that this is equal to T. Hence the numerical value of the intensity of the surface-tension is equal to the numerical value of the surface-energy per unit of surface. We must remember that since the film has two surfaces the surface-tension of the film is double the tension of the surface of the liquid of which it is formed.

To determine the relation between the surface-tension and the pressure which balances it when the form of the surface is not spherical, let us consider the following case:—

Let fig. 9 represent a section through the axis Cc of a soap-bubble in the form of a figure of revolution bounded by two circular disks AB and ab, and having the meridian section APa. Let PQ Non-spherical soap bubble. be an imaginary section normal to the axis. Let the radius of this section PR be y, and let PT, the tangent at P, make an angle a with the axis.

Let us consider the stresses which are exerted across this imaginary section by the lower part on the upper part. If the internal pressure exceeds the external pressure by p, there is in the first place a force πy²p acting upwards arising from the pressure p over the area of the section. In the next place, there is the surface-tension acting downwards, but at an angle a with the vertical, across the circular section of the bubble itself, whose circumference is 2πy, and the downward force is therefore 2πyT cos a.

Now these forces are balanced by the external force which acts on the disk ACB, which we may call F. Hence equating the forces which act on the portion included between ACB and PRQ

πy²p − 2πyT cos α = −F     (9).

If we make CR = z, and suppose z to vary, the shape of the bubble of course remaining the same, the values of y and of a will change, but the other quantities will be constant. In studying these variations we may if we please take as our independent variable the length s of the meridian section AP reckoned from A. Differentiating equation 9 with respect to s we obtain, after dividing by 2π as a common factor,

Now

The radius of curvature of the meridian section is

The radius of curvature of a normal section of the surface at right angles to the meridian section is equal to the part of the normal cut off by the axis, which is

R2 = PN = y/cos α     (13).

Hence dividing equation 10 by y sin α, we find

p = T(1/R1 + 1/R2)     (14).

This equation, which gives the pressure in terms of the principal radii of curvature, though here proved only in the case of a surface of revolution, must be true of all surfaces. For the curvature of any surface at a given point may be completely defined in terms of the positions of its principal normal sections and their radii of curvature.

Before going further we may deduce from equation 9 the nature of all the figures of revolution which a liquid film can assume. Let us first determine the nature of a curve, such that if it is rolled on the axis its origin will trace out the meridian section of the bubble. Since at any instant the rolling curve is rotating about the point of contact with the axis, the line drawn from this point of contact to the tracing point must be normal to the direction of motion of the tracing point. Hence if N is the point of contact, NP must be normal to the traced curve. Also, since the axis is a tangent to the rolling curve, the ordinate PR is the perpendicular from the tracing point P on the tangent. Hence the relation between the radius vector and the perpendicular on the tangent of the rolling curve must be identical with the relation between the normal PN and the ordinate PR of the traced curve. If we write r for PN, then y = r cos α, and equation 9 becomes

This relation between y and r is identical with the relation between the perpendicular from the focus of a conic section on the tangent at a given point and the focal distance of that point, provided the transverse and conjugate axes of the conic are 2a and 2b respectively, where

Hence the meridian section of the film may be traced by the focus of such a conic, if the conic is made to roll on the axis.

On the different Forms of the Meridian Line.—1. When the conic is an ellipse the meridian line is in the form of a series of waves, and the film itself has a series of alternate swellings and contractions as represented in figs. 9 and 10. This form of the film is called the unduloid.

1a. When the ellipse becomes a circle, the meridian line becomes a straight line parallel to the axis, and the film passes into the form of a cylinder of revolution.

1b. As the ellipse degenerates into the straight line joining its foci, the contracted parts of the unduloid become narrower, till at last the figure becomes a series of spheres in contact.

In all these cases the internal pressure exceeds the external by 2T/a where a is the semi-transverse axis of the conic. The resultant of the internal pressure and the surface-tension is equivalent to a tension along the axis, and the numerical value of this tension is equal to the force due to the action of this pressure on a circle whose diameter is equal to the conjugate axis of the ellipse.

2. When the conic is a parabola the meridian line is a catenary (fig. 11); the internal pressure is equal to the external pressure, and the tension along the axis is equal to 2πTm where m is the distance of the vertex from the focus.

3. When the conic is a hyperbola the meridian line is in the form of a looped curve (fig. 12). The corresponding figure of the film is called the nodoid. The resultant of the internal pressure and the surface-tension is equivalent to a pressure along the axis equal to that due to a pressure p acting on a circle whose diameter is the conjugate axis of the hyperbola.

When the conjugate axis of the hyperbola is made smaller and smaller, the nodoid approximates more and more to the series of spheres touching each other along the axis. When the conjugate axis of the hyperbola increases without limit, the loops of the nodoid are crowded on one another, and each becomes more nearly a ring of circular section, without, however, ever 269 reaching this form. The only closed surface belonging to the series is the sphere.

These figures of revolution have been studied mathematically by C.W.B. Poisson,3 Goldschmidt,4 L.L. Lindelöf and F.M.N. Moigno,5 C.E. Delaunay,6 A.H.E. Lamarle,7 A. Beer,8 and V.M.A. Mannheim,9 and have been produced experimentally by Plateau10 in the two different ways already described.

The limiting conditions of the stability of these figures have been studied both mathematically and experimentally. We shall notice only two of them, the cylinder and the catenoid.

Stability of the Cylinder.—The cylinder is the limiting form of the unduloid when the rolling ellipse becomes a circle. When the ellipse differs infinitely little from a circle, the equation of the meridian line becomes approximately y = a + c sin (x/a) where c is small. This is a simple harmonic wave-line, whose mean distance from the axis is a, whose wave-length is 2πa and whose amplitude is c. The internal pressure corresponding to this unduloid is as before p = T/a. Now consider a portion of a cylindric film of length x terminated by two equal disks of radius r and containing a certain volume of air. Let one of these disks be made to approach the other by a small quantity dx. The film will swell out into the convex part of an unduloid, having its largest section midway between the disks, and we have to determine whether the internal pressure will be greater or less than before. If A and C (fig. 13) are the disks, and if x the distance between the disks is equal to πr half the wave-length of the harmonic curve, the disks will be at the points where the curve is at its mean distance from the axis, and the pressure will therefore be T/r as before. If A1, C1 are the disks, so that the distance between them is less than πr, the curve must be produced beyond the disks before it is at its mean distance from the axis. Hence in this case the mean distance is less than r, and the pressure will be greater than T/r. If, on the other hand, the disks are at A2 and C2, so that the distance between them is greater than πr, the curve will reach its mean distance from the axis before it reaches the disks. The mean distance will therefore be greater than r, and the pressure will be less than T/r. Hence if one of the disks be made to approach the other, the internal pressure will be increased if the distance between the disks is less than half the circumference of either, and the pressure will be diminished if the distance is greater than this quantity. In the same way we may show that if the distance between the disks is increased, the pressure will be diminished or increased according as the distance is less or more than half the circumference of either.

Now let us consider a cylindric film contained between two equal fixed disks. A and B, and let a third disk, C, be placed midway between. Let C be slightly displaced towards A. If AC and CB are each less than half the circumference of a disk the pressure on C will increase on the side of A and diminish on the side of B. The resultant force on C will therefore tend to oppose the displacement and to bring C back to its original position. The equilibrium of C is therefore stable. It is easy to show that if C had been placed in any other position than the middle, its equilibrium would have been stable. Hence the film is stable as regards longitudinal displacements. It is also stable as regards displacements transverse to the axis, for the film is in a state of tension, and any lateral displacement of its middle parts would produce a resultant force tending to restore the film to its original position. Hence if the length of the cylindric film is less than its circumference, it is in stable equilibrium. But if the length of the cylindric film is greater than its circumference, and if we suppose the disk C to be placed midway between A and B, and to be moved towards A, the pressure on the side next A will diminish, and that on the side next B will increase, so that the resultant force will tend to increase the displacement, and the equilibrium of the disk C is therefore unstable. Hence the equilibrium of a cylindric film whose length is greater than its circumference is unstable. Such a film, if ever so little disturbed, will begin to contract at one secton and to expand at another, till its form ceases to resemble a cylinder, if it does not break up into two parts which become ultimately portions of spheres.

Instability of a Jet of Liquid.—When a liquid flows out of a vessel through a circular opening in the bottom of the vessel, the form of the stream is at first nearly cylindrical though its diameter gradually diminishes from the orifice downwards on account of the increasing velocity of the liquid. But the liquid after it leaves the vessel is subject to no forces except gravity, the pressure of the air, and its own surface-tension. Of these gravity has no effect on the form of the stream except in drawing asunder its parts in a vertical direction, because the lower parts are moving faster than the upper parts. The resistance of the air produces little disturbance until the velocity becomes very great. But the surface-tension, acting on a cylindric column of liquid whose length exceeds the limit of stability, begins to produce enlargements and contractions in the stream as soon as the liquid has left the orifice, and these inequalities in the figure of the column go on increasing till it is broken up into elongated fragments. These fragments as they are falling through the air continue to be acted on by surface-tension. They therefore shorten themselves, and after a series of oscillations in which they become alternately elongated and flattened, settle down into the form of spherical drops.

This process, which we have followed as it takes place on an individual portion of the falling liquid, goes through its several phases at different distances from the orifice, so that if we examine different portions of the stream as it descends, we shall find next the orifice the unbroken column, then a series of contractions and enlargements, then elongated drops, then flattened drops, and so on till the drops become spherical.

[The circumstances attending the resolution of a cylindrical jet into drops were admirably examined and described by F. Savart (“Mémoire sur la constitution des veines liquides lancées par des orifices circulaires en minces parois,” Ann. d. Chim. t. liii., 1833) and for the most part explained with great sagacity by Plateau. Let us conceive an infinitely long circular cylinder of liquid, at rest (a motion common to every part of the fluid is necessarily without influence upon the stability, and may therefore be left out of account for convenience of conception and expression), and inquire under what circumstances it is stable or unstable, for small displacements, symmetrical about the axis of figure.

Whatever the deformation of the originally straight boundary of the axial section may be, it can be resolved by Fourier’s theorem into deformations of the harmonic type. These component deformations are in general infinite in number, of very wave-length and of arbitrary phase; but in the first stages of the motion, with which alone we are at present concerned, each produces its effect independently of every other, and may be considered by itself. Suppose, therefore, that the equation of the boundary is

r = a + a cos kz,     (1)

where a is a small quantity, the axis of z being that of symmetry. 270 The wave-length of the disturbance may be called λ, and is connected with k by the equation k = 2π/λ. The capillary tension endeavours to contract the surface of the fluid; so that the stability, or instability, of the cylindrical form of equilibrium depends upon whether the surface (enclosing a given volume) be greater or less respectively after the displacement than before. It has been proved by Plateau (vide supra) that the surface is greater than before displacement if ka > 1, that is, if λ < 2πa; but less if ka < 1, or λ > 2πa. Accordingly, the equilibrium is stable if λ be less than the circumference; but unstable if λ be greater than the circumference of the cylinder. Disturbances of the former kind lead to vibrations of harmonic type, whose amplitudes always remain small; but disturbances, whose wave-length exceeds the circumference, result in a greater and greater departure from the cylindrical figure. The analytical expression for the motion in the latter case involves exponential terms, one of which (except in case of a particular relation between the initial displacements and velocities) increases rapidly, being equally multiplied in equal times. The coefficient (q) of the time in the exponential term (eqt) may be considered to measure the degree of dynamical instability; its reciprocal 1/q is the time in which the disturbance is multiplied in the ratio 1 : e.

The degree of instability, as measured by q, is not to be determined from statical considerations only; otherwise there would be no limit to the increasing efficiency of the longer wave-lengths. The joint operation of superficial tension and inertia in fixing the wave-length of maximum instability was first considered by Lord Rayleigh in a paper (Math. Soc. Proc., November 1878) on the “Instability of Jets.” It appears that the value of q may be expressed in the form

where, as before, T is the superficial tension, ρ the density, and F is given by the following table: —

The greatest value of F thus corresponds, not to a zero value of k²a², but approximately to k²a² = .4858, or to λ = 4.508 × 2a. Hence the maximum instability occurs when the wave-length of disturbance is about half as great again as that at which instability first commences.

Taking for water, in C.G.S. units, T = 81, ρ = 1, we get for the case of maximum instability

if d be the diameter of the cylinder. Thus, if d = 1, q-1 = .115; or for a diameter of one centimetre the disturbance is multiplied 2.7 times in about one-ninth of a second. If the disturbance be multiplied 1000 fold in time, t, qt = 3loge 10 = 6.9, so that t = .79d3/2. For example, if the diameter be one millimetre, the disturbance is multiplied 1000 fold in about one-fortieth of a second. In view of these estimates the rapid disintegration of a fine jet of water will not cause surprise.

The relative importance of two harmonic disturbances depends upon their initial magnitudes, and upon the rate at which they grow. When the initial values are very small, the latter consideration is much the more important; for, if the disturbances be represented by α1eq1t, α2eq2t, in which q1 exceeds q2, their ratio is (α1/α2)e−(q1 − q2)t; and this ratio decreases without limit with the time, whatever be the initial (finite) ratio α2 : α1. If the initial disturbances are small enough, that one is ultimately preponderant for which the measure of instability is greatest. The smaller the causes by which the original equilibrium is upset, the more will the cylindrical mass tend to divide itself regularly into portions whose length is equal to 4.5 times the diameter. But a disturbance of less favourable wave-length may gain the preponderance in case its magnitude be sufficient to produce disintegration in a less time than that required by the other disturbances present.

The application of these results to actual jets presents no great difficulty. The disturbances by which equilibrium is upset are impressed upon the fluid as it leaves the aperture, and the continuous portion of the jet represents the distance travelled during the time necessary to produce disintegration. Thus the length of the continuous portion necessarily depends upon the character of the disturbances in respect of amplitude and wave-length. It may be increased considerably, as F. Savart showed, by a suitable isolation of the reservoir from tremors, whether due to external sources or to the impact of the jet itself in the vessel placed to receive it. Nevertheless it does not appear to be possible to carry the prolongation very far. Whether the residuary disturbances are of external origin, or are due to friction, or to some peculiarity of the fluid motion within the reservoir, has not been satisfactorily determined. On this point Plateau’s explanations are not very clear, and he sometimes expresses himself as if the time of disintegration depended only upon the capillary tension, without reference to initial disturbances at all.

Two laws were formulated by Savart with respect to the length of the continuous portion of a jet, and have been to a certain extent explained by Plateau. For a given fluid and a given orifice the length is approximately proportional to the square root of the head. This follows at once from theory, if it can be assumed that the disturbances remain always of the same character, so that the time of disintegration is constant. When the head is given, Savart found the length to be proportional to the diameter of the orifice. From (3) it appears that the time in which a disturbance is multiplied in a given ratio varies, not as d, but as d3/2. Again, when the fluid is changed, the time varies as ρ1/2T −1/2. But it may be doubted whether the length of the continuous portion obeys any very simple laws, even when external disturbances are avoided as far as possible.

When the circumstances of the experiment are such that the reservoir is influenced by the shocks due to the impact of the jet, the disintegration usually establishes itself with complete regularity, and is attended by a musical note (Savart). The impact of the regular series of drops which is at any moment striking the sink (or vessel receiving the water), determines the rupture into similar drops of the portion of the jet at the same moment passing the orifice. The pitch of the note, though not absolutely definite, cannot differ much from that which corresponds to the division of the jet into wave-lengths of maximum instability; and, in fact, Savart found that the frequency was directly as the square root of the head, inversely as the diameter of the orifice, and independent of the nature of the fluid—laws which follow immediately from Plateau’s theory.

From the pitch of the note due to a jet of given diameter, and issuing under a given head, the wave-length of the nascent divisions can be at once deduced. Reasoning from some observations of Savart, Plateau finds in this way 4.38 as the ratio of the length of a division to the diameter of the jet. The diameter of the orifice was 3 millims., from which that of the jet is deduced by the introduction of the coefficient .8. Now that the length of a division has been estimated a priori, it is perhaps preferable to reverse Plateau’s calculation, and to exhibit the frequency of vibration in terms of the other data of the problem. Thus

But the most certain method of obtaining complete regularity of resolution is to bring the reservoir under the influence of an external vibrator, whose pitch is approximately the same as that proper to the jet. H.G. Magnus (Pogg. Ann. cvi., 1859) employed a Neef’s hammer, attached to the wooden frame which supported the reservoir. Perhaps an electrically maintained tuning-fork is still better. Magnus showed that the most important part of the effect is due to the forced vibration of that side of the vessel which contains the orifice, and that but little 271 of it is propagated through the air. With respect to the limits of pitch, Savart found that the note might be a fifth above, and more than an octave below, that proper to the jet. According to theory, there would be no well-defined lower limit; on the other side, the external vibration cannot be efficient if it tends to produce divisions whose length is less than the circumference of the jet. This would give for the interval defining the upper limit π : 4.508, which is very nearly a fifth. In the case of Plateau’s numbers (π : 4.38) the discrepancy is a little greater.

The detached masses into which a jet is resolved do not at once assume and retain a spherical form, but execute a series of vibrations, being alternately compressed and elongated in the direction of the axis of symmetry. When the resolution is effected in a perfectly periodic manner, each drop is in the same phase of its vibration as it passes through a given point of space; and thence arises the remarkable appearance of alternate swellings and contractions described by Savart. The interval from one swelling to the next is the space described by the drop during one complete vibration, and is therefore (as Plateau shows) proportional ceteris paribus to the square root of the head.

The time of vibration is of course itself a function of the nature of the fluid and of the size of the drop. By the method of dimensions alone it may be seen that the time of infinitely small vibrations varies directly as the square root of the mass of the sphere and inversely as the square root of the capillary tension; and it may be proved that its expression is

V being the volume of the vibrating mass.

In consequence of the rapidity of the motion some optical device is necessary to render apparent the phenomena attending the disintegration of a jet. Magnus employed a rotating mirror, and also a rotating disk from which a fine slit was cut out. The readiest method of obtaining instantaneous illumination is the electric spark, but with this Magnus was not successful. The electric spark had, however, been used successfully for this purpose some years before by H. Buff (Liebigs Ann. lxxviii. 1851), who observed the shadow of the jet on a white screen. Preferable to an opaque screen is a piece of ground glass, which allows the shadow to be examined from the farther side (Lord Rayleigh). Further, the jet may be very well observed directly, if the illumination is properly managed. For this purpose it is necessary to place it between the source of light and the eye. The best effect is obtained when the light of the spark is somewhat diffused by being passed (for example) through a piece of ground glass.

The spark may be obtained from the secondary of an induction coil, whose terminals are in connexion with the coatings of a Leyden jar. By adjustment of the contact breaker the series of sparks may be made to fit more or less perfectly with the formation of the drops. A still greater improvement may be effected by using an electrically maintained fork, which performs the double office of controlling the resolution of the jet and of interrupting the primary current of the induction coil. In this form the experiment is one of remarkable beauty. The jet, illuminated only in one phase of transformation, appears almost perfectly steady, and may be examined at leisure. In one experiment the jet issued horizontally from an orifice of about half a centimetre in diameter, and almost immediately assumed a rippled outline. The gradually increasing amplitude of the disturbance, the formation of the elongated ligament, and the subsequent transformation of the ligament into a spherule, could be examined with ease. In consequence of the transformation being in a more advanced stage at the forward than at the hinder end, the ligament remains for a moment connected with the mass behind, when it has freed itself from the mass in front, and thus the resulting spherule acquires a backwards relative velocity, which of necessity leads to a collision. Under ordinary circumstances the spherule rebounds, and may be thus reflected backwards and forwards several times between the adjacent masses. Magnus showed that the stream of spherules may be diverted into another path by the attraction of a powerfully electrified rod, held a little below the place of resolution.

Very interesting modifications of these phenomena are observed when a jet from an orifice in a thin plate (Tyndall has shown that a pinhole gas burner may also be used with advantage) is directed obliquely upwards. In this case drops which break away with different velocities are carried under the action of gravity into different paths; and thus under ordinary circumstances a jet is apparently resolved into a “sheaf,” or bundle of jets all lying in one vertical plane. Under the action of a vibrator of suitable periodic time the resolution is regularized, and then each drop, breaking away under like conditions, is projected with the same velocity, and therefore follows the same path. The apparent gathering together of the sheaf into a fine and well-defined stream is an effect of singular beauty.

In certain cases where the tremor to which the jet is subjected is compound, the single path is replaced by two, three or even more paths, which the drops follow in a regular cycle. The explanation has been given with remarkable insight by Plateau. If, for example, besides the principal disturbance, which determines the size of the drops, there be another of twice the period, it is clear that the alternate drops break away under different conditions and therefore with different velocities. Complete periodicity is only attained after the passage of a pair of drops; and thus the odd series of drops pursues one path, and the even series another.

Electricity, as has long been known, has an extraordinary influence upon the appearance of a fine jet of water ascending in a nearly perpendicular direction. In its normal state the jet resolves itself into drops, which even before passing the summit, and still more after passing it, are scattered through a considerable width. When a feebly electrified body (such as a stick of sealing-wax gently rubbed upon the coat sleeve) is brought into its neighbourhood, the jet undergoes a remarkable transformation and appears to become coherent; but under more powerful electrical action the scattering becomes even greater than at first. The second effect is readily attributed to the mutual repulsion of the electrified drops, but the action of feeble electricity in producing apparent coherence was long unexplained.

It was shown by W. von Beetz that the coherence is apparent only, and that the place where the jet breaks into drops is not perceptibly shifted by the electricity. By screening the various parts with metallic plates in connexion with earth, Beetz further proved that, contrary to the opinion of earlier observers, the seat of sensitiveness is not at the root of the jet where it leaves the orifice, but at the place of resolution into drops. An easy way of testing this conclusion is to excite the extreme tip of a glass rod, which is then held in succession to the root of the jet, and to the place of resolution. An effect is observed in the latter, and not in the former position.

The normal scattering of a nearly vertical jet is due to the rebound of the drops when they come into collision with one another. Such collisions are inevitable in consequence of the different velocities acquired by the drops under the action of the capillary force, as they break away irregularly from the continuous portion of the jet. Even when the resolution is regularized by the action of external vibrations of suitable frequency, as in the beautiful experiments of Savart and Plateau, the drops must still come into contact before they reach the summit of their parabolic path. In the case of a continuous jet, the equation of continuity shows that as the jet loses velocity in ascending, it must increase in section. When the stream consists of drops following one another in single file, no such increase of section is possible; and then the constancy of the total stream requires a gradual approximation of the drops, which in the case of a nearly vertical direction of motion cannot stop short of actual contact. Regular vibration has, however, the effect of postponing the collisions and consequent scattering of the drops, and in the case of a direction of motion less nearly vertical, may prevent them altogether.

Under moderate electrical influence there is no material 272 change in the resolution into drops, nor in the subsequent motion of the drops up to the moment of collision. The difference begins here. Instead of rebounding after collision, as the unelectrified drops of clean water generally, or always, do, the electrified drops coalesce, and then the jet is no longer scattered about. When the electrical influence is more powerful, the repulsion between the drops is sufficient to prevent actual contact, and then, of course, there is no opportunity for amalgamation.

These experiments may be repeated with extreme ease, and with hardly any apparatus. The diameter of the jet may be about 1⁄20 in., and it may issue from a glass nozzle. The pressure may be such as to give a fountain about 2 ft. high. The change in the sound due to the falling drops as they strike the bottom of the sink should be noticed, as well as that in the appearance of the jet.

The actual behaviour of the colliding drops becomes apparent under instantaneous illumination, e.g. by sparks from a Leyden jar. The jet should be situated between the sparks and the eye, and the observation is facilitated by a piece of ground glass held a little beyond the jet, so as to diffuse the light; or the shadow of the jet may be received on the ground glass, which is then held as close as possible on the side towards the observer.

In another form of the experiment, which, though perhaps less striking to the eye, lends itself better to investigation, the collision takes place between two still unresolved jets issuing horizontally from glass nozzles in communication with reservoirs containing water. One at least of the reservoirs must be insulated. In the absence of dust and greasy contamination, the obliquely colliding jets may rebound from one another without coalescence for a considerable time. In this condition there is complete electrical insulation between the jets, as may be proved by the inclusion in the circuit of a delicate galvanometer, and a low electromotive force. But if the difference of potential exceed a small amount (1 or 2 volts), the jets instantaneously coalesce. There is no reason to doubt that in the case of the fountain also, coalescence is due to differences of potential between colliding drops.

If the water be soapy, and especially if it contain a small proportion of milk, coalescence ensues without the help of electricity. In the case of the fountain the experiment may be made by leading tap-water through a Woulfe’s bottle in which a little milk has been placed. As the milk is cleared out, the scattering of the drops is gradually re-established.

In attempting to explain these curious phenomena, it is well to consider what occurs during a collision. As the liquid masses approach one another, the intervening air has to be squeezed out. In the earlier stages of approximation the obstacle thus arising may not be important; but when the thickness of the layer of air is reduced to the point at which the colours of thin plates are visible, the approximation must be sensibly resisted by the viscosity of the air which still remains to be got rid of. No change in the capillary conditions can arise until the interval is reduced to a small fraction of a wave-length of light; but such a reduction, unless extremely local, is strongly opposed by the remaining air. It is true that this opposition is temporary. The question is whether the air can everywhere be squeezed out during the short time over which the collision extends.

It would seem that the forces of electrical attraction act with peculiar advantage. If we suppose that upon the whole the air cannot be removed, so that the mean distance between the opposed surfaces remains constant, the electric attractions tend to produce an instability whereby the smaller intervals are diminished while the larger are increased. Extremely local contacts of the liquids, while opposed by capillary tension which tends to keep the surfaces flat, are thus favoured by the electrical forces, which moreover at the small distances in question act with exaggerated power.

A question arises as to the mode of action of milk or soap turbidity. The observation that it is possible for soap to be in excess may here have significance. It would seem that the surfaces, coming into collision within a fraction of a second of their birth, would still be subject to further contamination from the interior. A particle of soap rising accidentally to the surface would spread itself with rapidity. Now such an outward movement of the liquid is just what is required to hasten the removal of intervening air. It is obvious that the effect would fail if the contamination of the surface had proceeded too far previously to the collision.

This view is confirmed by experiments in which other gases are substituted for air as the environment of colliding jets. Oxygen and coal-gas were found to be without effect. On the other hand, the more soluble gases, carbon dioxide, nitrous oxide, sulphur dioxide, and steam, at once caused union.]

Stability of the Catenoid.—When the internal pressure is equal to the external, the film forms a surface of which the mean curvature at every point is zero. The only surface of revolution having this property is the catenoid formed by the revolution of a catenary about its directrix. This catenoid, however, is in stable equilibrium only when the portion considered is such that the tangents to the catenary at its extremities intersect before they reach the directrix.

To prove this, let us consider the catenary as the form of equilibrium of a chain suspended between two fixed points A and B. Suppose the chain hanging between A and B to be of very great length, then the tension at A or B will be very great. Let the chain be hauled in over a peg at A. At first the tension will diminish, but if the process be continued the tension will reach a minimum value and will afterwards increase to infinity as the chain between A and B approaches to the form of a straight line. Hence for every tension greater than the minimum tension there are two catenaries passing through A and B. Since the tension is measured by the height above the directrix these two catenaries have the same directrix. Every catenary lying between them has its directrix higher, and every catenary lying beyond them has its directrix lower than that of the two catenaries.

Now let us consider the surfaces of revolution formed by this system of catenaries revolving about the directrix of the two catenaries of equal tension. We know that the radius of curvature of a surface of revolution in the plane normal to the meridian plane is the portion of the normal intercepted by the axis of revolution.

The radius of curvature of a catenary is equal and opposite to the portion of the normal intercepted by the directrix of the catenary. Hence a catenoid whose directrix coincides with the axis of revolution has at every point its principal radii of curvature equal and opposite, so that the mean curvature of the surface is zero.

The catenaries which lie between the two whose direction coincides with the axis of revolution generate surfaces whose radius of curvature convex towards the axis in the meridian plane is less than the radius of concave curvature. The mean curvature of these surfaces is therefore convex towards the axis. The catenaries which lie beyond the two generate surfaces whose radius of curvature convex towards the axis in the meridian plane is greater than the radius of concave curvature. The mean curvature of these surfaces is, therefore, concave towards the axis.

Now if the pressure is equal on both sides of a liquid film, and if its mean curvature is zero, it will be in equilibrium. This is the case with the two catenoids. If the mean curvature is convex towards the axis the film will move from the axis. Hence if a film in the form of the catenoid which is nearest the axis is ever so slightly displaced from the axis it will move farther from the axis till it reaches the other catenoid.

If the mean curvature is concave towards the axis the film will tend to approach the axis. Hence if a film in the form of the catenoid which is nearest the axis be displaced towards the axis, it will tend to move farther towards the axis and will collapse. Hence the film in the form of the catenoid which is nearest the axis is in unstable equilibrium under the condition that it is exposed to equal pressures within and without. If, however, the circular ends of the catenoid are closed with solid disks, so that the volume of air contained between these disks and the film is determinate, the film will be in stable equilibrium however large a portion of the catenary it may consist of.

273

The criterion as to whether any given catenoid is stable or not may be obtained as follows:—

Let PABQ and ApqB (fig. 14) be two catenaries having the same directrix and intersecting in A and B. Draw Pp and Qq touching both catenaries, Pp and Qq will intersect at T, a point in the directrix; for since any catenary with its directrix is a similar figure to any other catenary with its directrix, if the directrix of the one coincides with that of the other the centre of similitude must lie on the common directrix. Also, since the curves at P and p are equally inclined to the directrix, P and p are corresponding points and the line Pp must pass through the centre of similitude. Similarly Qq must pass through the centre of similitude. Hence T, the point of intersection of Pp and Qq, must be the centre of similitude and must be on the common directrix. Hence the tangents at A and B to the upper catenary must intersect above the directrix, and the tangents at A and B to the lower catenary must intersect below the directrix. The condition of stability of a catenoid is therefore that the tangents at the extremities of its generating catenary must intersect before they reach the directrix.

Stability of a Plane Surface.—We shall next consider the limiting conditions of stability of the horizontal surface which separates a heavier fluid above from a lighter fluid below. Thus, in an experiment of F. Duprez (“Sur un cas particulier de l’équilibre des liquides,” Nouveaux Mém. del’ Acad. de Belgique, 1851 et 1853), a vessel containing olive oil is placed with its mouth downwards in a vessel containing a mixture of alcohol and water, the mixture being denser than the oil. The surface of separation is in this case horizontal and stable, so that the equilibrium is established of itself. Alcohol is then added very gradually to the mixture till it becomes lighter than the oil. The equilibrium of the fluids would now be unstable if it were not for the tension of the surface which separates them, and which, when the orifice of the vessel is not too large, continues to preserve the stability of the equilibrium.

When the equilibrium at last becomes unstable, the destruction of equilibrium takes place by the lighter fluid ascending in one part of the orifice and the heavier descending in the other. Hence the displacement of the surface to which we must direct our attention is one which does not alter the volume of the liquid in the vessel, and which therefore is upward in one part of the surface and downward in another. The simplest case is that of a rectangular orifice in a horizontal plane, the sides being a and b.

Let the surface of separation be originally in the plane of the orifice, and let the co-ordinates x and y be measured from one corner parallel to the sides a and b respectively, and let z be measured upwards. Then if ρ be the density of the upper liquid, and σ that of the lower liquid, and P the original pressure at the surface of separation, then when the surface receives an upward displacement z, the pressure above it will be P − ρgz, and that below it will be P − σgz, so that the surface will be acted on by an upward pressure (ρ − σ)gz. Now if the displacement z be everywhere very small, the curvature in the planes parallel to xz and yz will be d²z/dx² and d²z/dy² respectively, and if T is the surface-tension the whole upward force will be

If this quantity is of the same sign as z, the displacement will be increased, and the equilibrium will be unstable. If it is of the opposite sign from z, the equilibrium will be stable. The limiting condition may be found by putting it equal to zero. One form of the solution of the equation, and that which is applicable to the case of a rectangular orifice, is

z = C sin px sin qy.

Substituting in the equation we find the condition

That the surface may coincide with the edge of the orifice, which is a rectangle, whose sides are a and b, we must have

pa = mπ,   qb = nπ,

when m and n are integral numbers. Also, if m and n are both unity, the displacement will be entirely positive, and the volume of the liquid will not be constant. That the volume may be constant, either n or m must be an even number. We have, therefore, to consider the conditions under which

cannot be made negative. Under these conditions the equilibrium is stable for all small displacements of the surface. The smallest admissible value of m²/a² + n²/b² is 4/a² + 1/b², where a is the longer side of the rectangle. Hence the condition of stability is that

is a positive quantity. When the breadth b is less than √[π²T/(ρ − σ)g] the length a may be unlimited.

When the orifice is circular of radius a, the limiting value of a is √[(T/gρ)z], where z is the least root of the equation

The least root of this equation is

z = 3.83171.

If h is the height to which the liquid will rise in a capillary tube of unit radius, then the diameter of the largest orifice is

2a = 3.83171 √(2h) = 5.4188 √(h).

Duprez found from his experiments

2a = 5.485√(h).

[The above theory may be well illustrated by a lecture experiment. A thin-walled glass tube of internal diameter equal to 14½ mm. is ground true at the lower end. The upper end is contracted and is fitted with a rubber tube under the control of a pinch-cock. Water is sucked up from a vessel of moderate size, the rubber is nipped, and by a quick motion the tube and vessel are separated, preferably by a downward movement of the latter. The inverted tube, with its suspended water, being held in a clamp, a beaker containing a few drops of ether is brought up from below until the free surface of the water is in contact with ether vapour. The lowering of tension, which follows the condensation of the vapour, is then strikingly shown by the sudden precipitation of the water.]

Effect of Surface-tension on the Velocity of Waves.—When a series of waves is propagated on the surface of a liquid, the surface-tension has the effect of increasing the pressure at the crests of the waves and diminishing it in the troughs. If the wave-length is λ, the equation of the surface is

The pressure due to the surface tension T is

This pressure must be added to the pressure due to gravity gρy. Hence the waves will be propagated as if the intensity of gravity had been

instead of g. Now it is shown in hydrodynamics that the velocity of propagation of waves in deep water is that acquired by a heavy body falling through half the radius of the circle whose circumference is the wave-length, or

This velocity is a minimum when

and the minimum value is

For waves whose length from crest to crest is greater than λ, the principal force concerned in the motion is that of gravitation. 274 For waves whose length is less than λ the principal force concerned is that of surface-tension. Lord Kelvin proposed to distinguish the latter kind of waves by the name of ripples.

When a small body is partly immersed in a liquid originally at rest, and moves horizontally with constant velocity V, waves are propagated through the liquid with various velocities according to their respective wave-lengths. In front of the body the relative velocity of the fluid and the body varies from V where the fluid is at rest, to zero at the cutwater on the front surface of the body. The waves produced by the body will travel forwards faster than the body till they reach a distance from it at which the relative velocity of the body and the fluid is equal to the velocity of propagation corresponding to the wave-length. The waves then travel along with the body at a constant distance in front of it. Hence at a certain distance in front of the body there is a series of waves which are stationary with respect to the body. Of these, the waves of minimum velocity form a stationary wave nearest to the front of the body. Between the body and this first wave the surface is comparatively smooth. Then comes the stationary wave of minimum velocity, which is the most marked of the series. In front of this is a double series of stationary waves, the gravitation waves forming a series increasing in wave-length with their distance in front of the body, and the surface-tension waves or ripples diminishing in wave-length with their distance from the body, and both sets of waves rapidly diminishing in amplitude with their distance from the body.

If the current-function of the water referred to the body considered as origin is ψ, then the equation of the form of the crest of a wave of velocity w, the crest of which travels along with the body, is

dψ = w ds

where ds is an element of the length of the crest. To integrate this equation for a solid of given form is probably difficult, but it is easy to see that at some distance on either side of the body, where the liquid is sensibly at rest, the crest of the wave will approximate to an asymptote inclined to the path of the body at an angle whose sine is w/V, where w is the velocity of the wave and V is that of the body.

The crests of the different kinds of waves will therefore appear to diverge as they get farther from the body, and the waves themselves will be less and less perceptible. But those whose wave-length is near to that of the wave of minimum velocity will diverge less than any of the others, so that the most marked feature at a distance from the body will be the two long lines of ripples of minimum velocity. If the angle between these is 2θ, the velocity of the body is w sec θ, where w for water is about 23 centimetres per second.

[Lord Kelvin’s formula (1) may be applied to find the surface-tension of a clean or contaminated liquid from observations upon the length of waves of known periodic time, travelling over the surface. If v = λ/τ we have

h denoting the depth of the liquid. In observations upon ripples the factor involving h may usually be omitted, and thus in the case of water (ρ = 1)

simply. The method has the advantage of independence of what may occur at places where the liquid is in contact with solid bodies.

The waves may be generated by electrically maintained tuning-forks from which dippers touch the surface; but special arrangements are needed for rendering them visible. The obstacles are (1) the smallness of the waves, and (2) the changes which occur at speeds too rapid for the eye to follow. The second obstacle is surmounted by the aid of the stroboscopic method of observation, the light being intermittent in the period of vibration, so that practically only one phase is seen. In order to render visible the small waves employed, and which we may regard as deviations of a plane surface from its true figure, the method by which Foucault tested reflectors is suitable. The following results have been obtained

(Phil. Mag. November 1890) for the tensions of various water-surfaces at 18° C., reckoned in C.G.S. measure.

The tension for clean water thus found is considerably lower than that (81) adopted by Quincke, but it seems to be entitled to confidence, and at any rate the deficiency is not due to contamination of the surface.

A calculation analogous to that of Lord Kelvin may be applied to find the frequency of small transverse vibrations of a cylinder of liquid under the action of the capillary force. Taking the case where the motion is strictly in two dimensions, we may write as the polar equation of the surface at time t

r = a + αn cos nθ cos pt,     (4)

where p is given by

If n = 1, the section remains circular, there is no force of restitution, and p = 0. The principal vibration, in which the section becomes elliptical, corresponds to n = 2.

Vibrations of this kind are observed whenever liquid issues from an elliptical or other non-circular hole, or even when it is poured from the lip of an ordinary jug; and they are superposed upon the general progressive motion. Since the phase of vibration depends upon the time elapsed, it is always the same at the same point in space, and thus the motion is steady in the hydrodynamical sense, and the boundary of the jet is a fixed surface. In so far as the vibrations may be regarded as isochronous, the distance between consecutive corresponding points of the recurrent figure, or, as it may be called, the wave-length of the figure, is directly proportional to the velocity of the jet, i.e. to the square root of the head. But as the head increases, so do the lateral velocities which go to form the transverse vibrations. A departure from the law of isochronism may then be expected to develop itself.

The transverse vibrations of non-circular jets allow us to solve a problem which at first sight would appear to be of great difficulty. According to Marangoni the diminished surface-tension of soapy water is due to the formation of a film. The formation cannot be instantaneous, and if we could measure the tension of a surface not more than 1⁄100 of a second old, we might expect to find it undisturbed, or nearly so, from that proper to pure water. In order to carry out the experiment the jet is caused to issue from an elliptical orifice in a thin plate, about 2 mm. by 1 mm., under a head of 15 cm. A comparison under similar circumstances shows that there is hardly any difference in the wave-lengths of the patterns obtained with pure and with soapy water, from which we conclude that at this initial stage, the surface-tensions are the same. As early as 1869 Dupré had arrived at a similar conclusion from experiments upon the vertical rise of fine jets.

A formula, similar to (5), may be given for the frequencies of vibration of a spherical mass of liquid under capillary force. If, as before, the frequency be p/2Π, and a the radius of the sphere, we have

n denoting the order of the spherical harmonic by which the deviation from a spherical figure is expressed. To find the radius of the sphere of water which vibrates seconds, put p = 2Π, T = 81, ρ = 1, n = 2. Thus a = 2.54 cms., or one inch very nearly.]

Tables of Surface-tension

In the following tables the units of length, mass and time are the centimetre, the gramme and the second, and the unit of force is that which if it acted on one gramme for one second would communicate to it a velocity of one centimetre per second:—

275

Table of Surface-Tension at 20° C. (Quincke).

Quincke has determined the surface-tension of a great many substances near their point of fusion or solidification. His method was that of observing the form of a large drop standing on a plane surface. If K is the height of the flat surface of the drop, and k that of the point where its tangent plane is vertical, then

T = ½(K − k)²gρ

Quincke finds that for several series of substances the surface-tension is nearly proportional to the density, so that if we call (K - k)² = 2T/gρ the specific cohesion, we may state the general results of his experiments as follows:—

Surface-Tensions of Liquids at their Point of Solidification. From Quincke.

The bromides and iodides have a specific cohesion about half that of mercury. The nitrates, chlorides, sugars and fats, as also the metals lead, bismuth and antimony, have a specific cohesion nearly equal to that of mercury. Water, the carbonates and sulphates, and probably phosphates, and the metals platinum, gold, silver, cadmium, tin and copper have a specific cohesion double that of mercury. Zinc, iron and palladium, three times that of mercury, and sodium, six times that of mercury.

Relation of Surface-tension to Temperature

It appears from the experiments of Brunner and of Wolf on the ascent of water in tubes that at the temperature t° centigrade

Lord Kelvin has applied the principles of Thermodynamics to determine the thermal effects of increasing or diminishing the area of the free surface of a liquid, and has shown that in order to keep the temperature constant while the area of the surface increases by unity, an amount of heat must be supplied to the liquid which is dynamically equivalent to the product of the absolute temperature into the decrement of the surface-tension per degree of temperature. We may call this the latent heat of surface-extension.

It appears from the experiments of C. Brunner and C.J.E. Wolf that at ordinary temperatures the latent heat of extension of the surface of water is dynamically equivalent to about half the mechanical work done in producing the surface-extension.

CAPISTRANO, GIOVANNI DI (1386-1456), Italian friar, theologian and inquisitor, was born in the little village of Capistrano in the Abruzzi, of a family which had come to Italy with the Angevins. He lived at first a wholly secular life, married, and became a successful magistrate; he took part in the continual struggles of the small Italian states in such a way as to compromise himself. During his captivity he was practically ruined and lost his young wife. He then in despair entered the Franciscan order and at once gave himself up to the most rigorous asceticism, violently defending the ideal of strict observance. He was charged with various missions by the popes Eugenius IV. and Nicholas V., in which he acquitted himself with implacable violence. As legate or inquisitor he persecuted the last Fraticelli of Ferrara, the Jesuati of Venice, the Jews of Sicily, Moldavia and Poland, and, above all, the Hussites of Germany, Hungary and Bohemia; his aim in the last case was to make conferences impossible between the representatives of Rome and the Bohemians, for every attempt at conciliation seemed to him to be conniving at heresy. Finally, after the taking of Constantinople, he succeeded in gathering troops together for a crusade against the Turks (1455), which at least helped to raise the siege of Belgrade, which was being blockaded by Mahommed II. He died shortly afterwards (October 23, 1456), and was canonized in 1690. Capistrano, in spite of this restless life, found time to work both in the lifetime of his master St Bernardino of Siena and after, at the reform of the order of the minor Franciscans, and to uphold both in his writings and his speeches the most advanced theories upon the papal supremacy as opposed to that of the councils.

CAPITAL (Lat. caput, head), in architecture, the crowning member of the column, which projects on each side as it rises, in order to support the abacus and unite the square form of the latter with the circular shaft. The bulk of the capital may either be convex, as in the Doric capital; concave, as in the bell of the Corinthian capital; or bracketed out, as in the Ionic capital. These are the three principal types on which all capitals are based. The capitals of Greek, Doric, Ionic and Corinthian orders are given in the article Order.

From the prominent position it occupies in all monumental buildings, it has always been the favourite feature selected for ornamentation, and consequently it has become the clearest indicator of any style.

The two earliest capitals of importance are those which are based on the lotus (fig. 1) and papyrus (fig. 2) plants respectively, and these, with the palm tree capital, were the chief types employed by the Egyptians down to the 3rd century b.c., when, 276 under the Ptolemaic dynasties, various river plants were employed decoratively and the lotus capital goes through various modifications (fig 3) Some kind of volute capital is shown in the Assyrian bas-reliefs, but no Assyrian capital has ever been found, those exhibited as such in the British Museum are bases.

The Persian capital belongs to the third class above mentioned, the brackets are carved with the lion (fig. 4) or the griffin projecting right and left to support and lessen the bearing of the architrave, and on their backs carry other brackets at right angles to support the cross timbers. The profuse decoration underneath the bracket capital in the palace of Xerxes and elsewhere, serves no structural function, but gives some variety to the extenuated shaft.

The earliest Greek capital is that shown in the Temple-fresco at Cnossus in Crete (1600 b.c.); it was of the first type—convex, and was probably moulded in stucco: the second is represented by the richly carved example of the columns (fig 5) flanking the tomb of Agamemnon in Mycenae (c. 1100 b.c.), also convex, carved with the chevron device, and with an apophyge on which the buds of some flowers are sculptured. The Doric capital of the temple of Apollo at Syracuse (c. 700 b.c.) follows, in which the echinus moulding has become a more definite form: this in the Parthenon reaches its culmination, where the convexity is at the top and bottom with a delicate uniting curve The sloping side of the echinus becomes flatter in the later examples, and in the Colosseum at Rome forms a quarter round.

In the Ionic capital of the Archaic temple of Diana at Ephesus (560 b.c.) the width of the abacus is twice that of its depth, consequently the earliest Ionic capital known was virtually a bracket capital. A century later, in the temple on the Ilissus, published in Stuart and Revett, the abacus has become square. One of the most beautiful Corinthian capitals is that from the Tholos of Epidaurus (400 b.c.) (fig. 6); it illustrates the transition between the earlier Greek capital of Bassae and the Roman version of the temple of Mars Ultor (fig. 7).

The foliage of the Greek Corinthian capital was based on the Acanthus spinosus, that of the Roman on the Acanthus mollis; the capital of the temple of Vesta and other examples at Pompeii are carved with foliage of a different type.

Byzantine capitals are of endless variety; the Roman composite capital would seem to have been the favourite type they followed at first: subsequently, the block of stone was left rough as it came from the quarry, and the sculptor, set to carve it, evolved 277 new types of design to his own fancy, so that one rarely meets with many repetitions of the same design. One of the most remarkable is the capital in which the leaves are carved as if blown by the wind; the finest example being in Sta Sophia, Thessalonica; those in St Mark’s, Venice (fig. 8) specially attracted Ruskin’s fancy. Others are found in St Apollinare-in-classe, Ravenna. The Thistle and Pine capital is found in St Mark’s, Venice; St Luke’s, Delphi; the mosques of Kairawan and of Ibn Tūlūn, Cairo, in the two latter cases being taken from Byzantine churches. The illustration of the capital in S. Vitale, Ravenna (figs. 9 and 10) shows above it the dosseret required to carry the arch, the springing of which was much wider than the abacus of the capital.

The Romanesque and Gothic capitals throughout Europe present the same variety as in the Byzantine and for the same reason, that the artist evolved his conception of the design from the block he was carving, but in these styles it goes further on account of the clustering of columns and piers.

The earliest type of capital in Lombardy and Germany is that which is known as the cushion-cap, in which the lower portion of the cube block has been cut away to meet the circular shaft (fig. 11). These early types were generally painted at first with various geometrical designs, afterwards carved.

In Byzantine capitals, the eagle, the lion and the lamb are occasionally carved, but treated conventionally.

In the Romanesque and Gothic styles, in addition to birds and beasts, figures are frequently introduced into capitals, those in the Lombard work being rudely carved and verging on the grotesque; later, the sculpture reaches a higher standard; in the cloisters of Monreale (fig. 12) the birds being wonderfully true to nature. In England and France (figs. 13 and 14), the figures introduced into the capitals are sometimes full of character. These capitals, however, are not equal to those of the Early English school, in which the foliage is conventionally treated as if it had been copied from metal work, and is of infinite variety, being found in small village churches as well as in cathedrals.

Reference has only been made to the leading examples of the Roman capitals; in the Renaissance period (fig. 15) the feature became of the greatest importance and its variety almost as great as in the Byzantine and Gothic styles. The pilaster, which 278 was employed so extensively in the Revival, called for new combinations in the designs for its capitals. Most of the ornament can be traced to Roman sources, and although less vigorous, shows much more delicacy and refinement in its carving.

CAPITAL (i.e. capital stock or fund), in economics, generally, the accumulated wealth either of a man or a community, that is available for earning interest and producing fresh wealth. In social discussion it is sometimes treated as antithetical to labour, but it is in reality the accumulated savings of labour and of the profits accruing from the savings of labour. It is that portion of the annual produce reserved from consumption to supply future wants, to extend the sphere of production, to improve industrial instruments and processes, to carry out works of public utility, and, in short, to secure and enlarge the various means of progress necessary to an increasing community. It is the increment of wealth or means of subsistence analogous to the increment of population and of the wants of civilized man. Hence J.S. Mill and other economists, when seeking a graphic expression of the service of capital, have called it “abstinence.” The labourer serves by giving physical and mental effort in order to supply his means of consumption. The capitalist, or labourer-capitalist, serves by abstaining from consumption, by denying himself the present enjoyment of more or less of his means of consumption, in the prospect of a future profit. This quality, apparent enough in the beginnings of capital, applies equally to all its forms and stages; because whether a capitalist stocks his warehouse with goods and produce, improves land, lends on mortgage or other security, builds a factory, opens a mine, or orders the construction of machines or ships, there is the element of self-deprival for the present, with the risk of ultimate loss of what is his own, and what, instead of saving and embodying income productive form, he might choose to consume. On this ground rests the justification of the claims of capital to its industrial rewards, whether in the form of rent, interest or profits of trade and investment.

To any advance in the arts of industry or the comforts of life, a rate of production exceeding the rate of consumption, with consequent accumulation of resources, or in other words, the formation of capital, is indispensable. The primitive cultivators of the soil, whether those of ancient times or the pioneers who formed settlements in the forests of the New World, soon discovered that their labour would be rendered more effective by implements and auxiliary powers of various kinds, and that until the produce from existing means of cultivation exceeded what was necessary for their subsistence, there could be neither labour on their part to produce such implements and auxiliaries, nor means to purchase them. Every branch of industry has thus had a demand for capital within its own circles from the earliest times. The flint arrow-heads, the stone and bronze utensils of fossiliferous origin, and the rude implements of agriculture, war and navigation, of which we read in Homer, were the forerunners of that rich and wonderful display of tools, machines, engines, furnaces and countless ingenious and costly appliances, which represent so large a portion of the capital of civilized countries, and without the pre-existing capital could not have been developed. Nor in the cultivation of land, or the production simply of food, is the need of implements, and of other auxiliary power, whether animal or mechanical, the only need immediately experienced. The demands on the surplus of produce over consumption are various and incessant. Near the space of reclaimed ground, from which the cultivator derives but a bare livelihood, are some marshy acres that, if drained and enclosed, would add considerably in two or three years to the produce; the forest and other natural obstructions might also be driven farther back with the result, in a few more years, of profit; fences are necessary to allow of pasture and field crops, roads have to be made and farm buildings to be erected; as the work proceeds more artificial investments follow, and by these successive outlays of past savings in improvements, renewed and enhanced from generation to generation, the land, of little value in its natural state either to the owner and cultivator or the community, is at length brought into a highly productive condition. The history of capital in the soil is substantially the history of capital in all other spheres. No progress can be made in any sphere, small or large, without reserved funds possessed by few or more persons, in small or large amounts, and the progress in all cases is adventured under self-deprival in the meanwhile of acquired value, and more or less risk as to the final result.

Capital is necessarily to be distinguished from money, with which in ordinary nomenclature it is almost identical. Wealth may be in other things than money; oxen, wives, tools, have at different stages of civilization represented the recognized form of capital; and modern usage only treats capital as meaning the command of money because money is the ordinary form of it nowadays. The capital of a country can scarce be said to be less than the whole sum of its investments in a productive form, and possessing a recognized productive value.

Adam Smith’s distinction of “fixed” and “circulating” capital in the Wealth of Nations (book ii. c. i.) cannot fail to be always useful in exhibiting the various forms and conditions under which capital is employed. Yet the principal phenomena of capital are found to be the same, whether the form of investment be more or less permanent or circulable. The machinery in which capital is “fixed,” and which yields a profit without apparently changing hands, is in reality passing away day by day, until it is worn out, and has to be replaced. So also of drainage and other land improvements. When the natural forests have been consumed and the landowners begin to plant trees on the bare places, the plantations while growing are a source of health, shelter and embellishment—they are not without a material profit throughout their various stages to maturity—and when, at the lapse of twenty or more years, they are ready to be cut down, and the timber is sold for useful purposes, there is a harvest of the original capital expended as essentially as in the case of the more rapid yearly crops of wheat or oats. The chief distinction would appear to rest in the element of time elapsing between the outlay of capital and its return. Capital may be employed in short loans or bills of exchange at two or three months, in paying wages of labour for which there may be return in a day or not in less than a year or more, or in operations involving within themselves every form of capital expenditure, and requiring a few years or ninety-nine years for the promised fructification on which they proceed. But the common characteristic of capital is that of a fund yielding a return and reproducing itself whether the time to this end be long or short. The division of expenditure or labour (all expenditure having a destination to labour of one kind or another) into “productive” and “unproductive” by the same authority (book ii. c. 3) is also apposite both for purposes of political economy and practical guidance, though economists have found it difficult to define where “productive expenditure” ends and “unproductive expenditure” begins. Adam Smith includes in his enumeration of the “fixed capital” of a country “the acquired and useful abilities of all the inhabitants”; and in this sense expenditure on education, arts and sciences might be deemed expenditure of the most productive value, and yet be wanting in strict commercial account of the profit and loss. It must be admitted that there is a personal expenditure among all ranks of society, which, though not in any sense a capital expenditure, may become capital and receive a productive application, always to be preferred to the grossly unproductive form, in the interest both of the possessors and of the community.

279

CAPITAL PUNISHMENT. By this term is now meant the infliction of the penalty of death for crime under the sentence of some properly constituted authority, as distinguished from killing the offender as a matter of self-defence or private vengeance, or under the order of some self-constituted or irregular tribunal unknown to the law, such as that of the Vigilantes of California, or of lynch law (q.v.). In the early stages of society a man-slayer was killed by the “avenger of blood” on behalf of the family of the man killed, and not as representing the authority of the state (Pollock and Maitland, Hist. Eng. Law, ii. 447.) This mode of dealing with homicide survives in the vendetta of Corsica and of the Mainotes in Greece, and in certain of the southern states of North America. The obligation or inclination to take vengeance depends on the fact of homicide, and not on the circumstances in which it was committed, i.e. it is a part of the lex talionis. The mischief of this system was alleviated under the Levitical law by the creation of cities of refuge, and in Greece and Italy, both in Pagan and Christian times, by the recognition of the right of sanctuary in temples and churches. A second mode of dealing with homicide was that known to early Teutonic and early Celtic law, where the relatives of the deceased, instead of the life of the slayer, received the wer of the deceased, i.e. a payment in proportion to the rank of the slain, and the king received the blood-wite for the loss of his man. But even under this system certain crimes were in Anglo-Saxon law bot-less, i.e. no compensation could be paid, and the offender must suffer the penalty of death. In the laws of Khammurabi, king of Babylon (2285-2242 b.c.), the death penalty is imposed for many offences. The modes for executing it specially named are burning, drowning and impalement (Oldest Code of Laws, by C.H.W. Johns, 1903). Under the Roman law, “capital” punishment also included punishments which deprived the offender of the status of Roman citizen (capitis deminutio, capitis amissio), e.g. condemnation to servitude in the mines or to deportation to an island (Dig. 48. 19).

United Kingdom.—The modes of capital punishment in England under the Saxon and Danish kings were various: hanging, beheading, burning, drowning, stoning, and precipitation from rocks. The principle on which this British and foreign laws and methods. variety depended was that where an offence was such as to entitle the king to outlaw the offender, he forfeited all, life and limb, lands and goods, and that the king might take his life and choose the mode of death. William the Conqueror would not allow judgment of death to be executed by hanging and substituted mutilation; but his successors varied somewhat in their policy as to capital punishment, and by the 13th century the penalty of death became by usage (without legislation) the usual punishment for high and petty treason and for all felonies (except mayhem and petty larceny, i.e. theft of property worth less than 1s.); see Stephen, Hist. Cr. Law, vol. i. 458; Pollock and Maitland, Hist. Eng. Law, vol. ii. 459. It therefore included all the more serious forms of crime against person or property, such as murder, manslaughter, arson, highway robbery, burglary (or hamesucken) and larceny; and when statutory felonies were created they were also punishable by death unless the statute otherwise provided. The death penalty was also extended to heretics under the writ de heretico comburendo, which was lawfully issuable under statute from 1382 (5 Ric. II. stat. 5) until 1677 (29 Chas. II. c. 9). For this purpose the legislature had adopted the civil law of the Roman Empire, which was not a part of the English common law (Stephen, Hist. Cr. Law, vol. ii. 438-469).

The methods of execution by crucifixion (as under the Roman law), or breaking on the wheel (as under the Roman Dutch law and the Holy Roman Empire), were never recognized by the common law, and would fall within the term “cruel and unusual punishments” in the English Bill of Rights, and in the United States would seem to be unconstitutional (see Wilkinson v. Utah, 1889, 136 U.S. 436, 446).

The severity of barbarian and feudal laws was mitigated, so far as common-law offences were concerned, by the influence of the Church as the inheritor of Christian traditions and Roman jurisprudence. The Roman law under the empire did not allow the execution of citizens except under the Lex Porcia. But the right of the emperors to legislate per rescriptum principis enabled them to disregard the ordinary law when so disposed. The 83rd novel of Justinian provided that criminal causes against clerics should be tried by the judges, and that the convicted cleric should be degraded by his bishop before his condemnation by the secular power, and other novels gave the bishops considerable influence, if not authority, over the lay judiciary. In western Europe the right given by imperial legislation in the Eastern Empire was utilized by the Papacy to claim privilege of clergy, i.e. that clerks must be remitted to the bishop for canonical punishment, and not subjected to civil condemnation at all. The history of benefit of clergy is given in Pollock and Maitland, Hist. English Law, vol. i. pp. 424-440, and Stephen, Hist. Cr. Law, vol. iii. 459, 463. By degrees the privilege was extended not only to persons who could prove ordination or show a genuine tonsure, but all persons who had sufficient learning to be able to read the neck-verse (Ps. li. v. 1). Before the Reformation the ecclesiastical courts had ceased to take any effective action with respect to clerks accused of offences against the king’s laws; and by the time of Henry VII. burning on the hand under the order of the king’s judges was substituted for the old process of compurgation in use in the spiritual courts.

The effect of the claim of benefit of clergy is said to have been to increase the number of convictions, though it mitigated the punishment; and it became, in fact, a means of showing mercy to certain classes of individuals convicted of crime as a kind of privilege to the educated, i.e. to all clerks whether secular or religious (25 Edw. III. stat. 3); and it was allowed only in case of a first conviction, except in the case of clerks who could produce their letters of orders or a certificate of ordination. To prevent a second claim it was the practice to brand murderers with the letter M, and other felons with the Tyburn T, and Ben Jonson was in 1598 so marked for manslaughter.

The reign of Henry VIII. was marked by extreme severity in the execution of criminals—as during this time 72,000 persons are said to have been hanged. After the formation of English settlements in America the severity of the law was mitigated by the practice of reprieving persons sentenced to death on condition of their consenting to be transported to the American colonies, and to enter into bond service there. The practice seems to have been borrowed from Spain, and to have been begun in 1597 (39 Eliz. c. 4). It was applied by Cromwell after his campaign in Ireland, and was in full force immediately after the Restoration, and is recognized in the Habeas Corpus Act 1677, and was used for the Cameronians during Claverhouse’s campaign in south-west Scotland. In the 18th century the courts were empowered to sentence felons to transportation (see Deportation) instead of to execution, and this state of the law continued until 1857 (6 Law Quarterly Review, p. 388). This power to sentence to transportation at first applied only to felonies with benefit of clergy; but in 1705, on the abolition of the necessity of proving capacity to read, all criminals alike became entitled to the benefit previously reserved to clerks. Benefit of clergy was finally abolished in 1827 as to all persons not having privilege of peerage, and in 1841 as to peers and peeresses. Its beneficial effect had now been exhausted, since no clergyable offences remained capital crimes.

At the end of the 18th century the criminal law of all Europe was ferocious and indiscriminate in its administration of capital punishment for almost all forms of grave crime; and yet owing to poverty, social conditions, and the inefficiency of the police, such forms of crime were far more numerous than they now are. The policy and righteousness of the English law were questioned as early as 1766 by Goldsmith through the mouth of the vicar of Wakefield: “Nor can I avoid even questioning the validity of that right which social combinations have assumed of capitally punishing offences of a slight nature. In cases of murder their right is obvious, as it is the duty of us all from the law of self-defence to cut off that man who has shown a disregard for the 280 life of another. Against such all nature rises in arms; but it is not so against him who steals my property.” He adds later: “When by indiscriminate penal laws the nation beholds the same punishment affixed to dissimilar degrees of guilt, the people are led to lose all sense of distinction in the crime, and this distinction is the bulwark of all morality.”

The opinion expressed by Goldsmith was strongly supported by Bentham, Romilly, Basil Montaguand Mackintosh in England, and resulted in considerable mitigation of the severity of the law. In 1800 over 200 and in 1819 about 180 crimes were capital. As the result of the labour of these eminent men and their disciples, and of Sir Robert Peel, there are now only four crimes (other than offences against military law or naval discipline) capitally punishable in England—high treason, murder, piracy with violence, and destruction of public arsenals and dockyards (The Dockyards, &c., Protection Act 1772). An attempt to abolish the death penalty for this last offence was made in 1837, but failed, and has not since been renewed. In the case of the last two offences sentence of death need not be pronounced, but may be recorded (4 Geo. IV. c. 48). Since 1838 it has in practice been executed only for murder; the method being by hanging.

The change in the severity of the law is best illustrated by the following statistics:—

During the twelve years from 1893 to 1904, 788 persons were committed for trial for murder, being an average of 65. The highest number was in 1893 (82) and the lowest in 1900 (51). Of those tried in 1904, 28 (26 males and 2 females) were convicted of murder, 16 (all males) were executed; 9 males and 2 females had their sentences commuted to penal servitude for life.

In Scotland capital punishment can be imposed only for treason, murder and offences against 10 Geo. IV. c. 38, i.e., wilful shooting, stabbing, strangling or throwing corrosives with intent to murder, maim, disfigure, disable, or do grievous bodily harm, in all cases where if death had ensued the offence would have been murder. Prior to 1887 rape, robbery, wilful fire-raising and incest, and many other crimes, were also capital offences; but in practice the pains of law were restricted at the instance of the prosecution. The method is by hanging.

In Ireland capital punishment may be inflicted for the same offences as in England, except offences under the Dockyards Protection Act 1772, and it is carried out in the same manner.

Offences under Military Law.—Thus far only crimes against the ordinary law of the land have been dealt with. But both the Naval Discipline Act of 1866 and the Army Act empower courts-martial to pass sentence for a number of offences against military and naval laws. Such sentences are rarely if ever passed where an ordinary court is within reach, or except in time of war. The offences extend from traitorous communication with the enemy and cowardice on the field to falling asleep while acting as a sentinel on active service. It is for the authority confirming a sentence of death by court-martial to direct the mode of execution, which both in the British and United States armies is usually by shooting or hanging. During the Indian Mutiny some mutineers were executed by being blown from the mouth of cannon. As to the history of military punishments see Clode, Military and Martial Law.

British Colonies and Possessions.—Under the Indian Penal Code sentence of death may be passed for waging war against the king (s. 121) and for murder (s. 302). If the murder is committed by a man under sentence of transportation for life the death penalty must be imposed (s. 303). In other cases it is alternative. This code has been in substance adopted in Ceylon, in Straits Settlements and Hong-Kong, and in the Sudan. In most of the British colonies and possessions the death penalty may be imposed only in the case of high treason, wilful murder and piracy with violence. But in New South Wales and Victoria sentence of death may be passed for rape and criminal abuse of girls under ten. In Queensland the law was the same until the passing of the Criminal Code of 1899.

Under the Canadian Criminal Code of 1892 the death sentence may be imposed for treason (s. 657), murder (s. 231), rape (s. 267), piracy with violence (s. 127), and upon subjects of a friendly power who levy war on the king in Canada (s. 68). But the judge is bound by statute to report on all death sentences, and the date of execution is fixed so as to give time for considering the report. The sentence is executed by hanging. In South Africa the criminal law is based on the Roman-Dutch law, under which capital punishment is liable for treason (crimen perduellionis or laesae majestatis), murder and rape (van Lecuwen, c. 36). In the Cape Colony rape is still capital (R. v. Nonosi, 1885; 1 Buchanan, 1898). In Natal rape may be punished by hanging (act no. 22, 1898). Though the Roman-Dutch modes of executing the sentence by decapitation or breaking on the wheel have not been formally abolished, in practice the sentence in the Cape Colony is executed by hanging. In the Transvaal hanging is now the sole mode of executing capital punishment (Criminal Procedure Code, 1903, s. 244). The Roman-Dutch law as to crime and punishments has been superseded in Ceylon and British Guiana by ordinance.

Austria-Hungary.—In Austria capital punishment was in 1787 for a time abolished, but was reintroduced in 1795 for high treason, and in 1803 for certain other crimes. Under the penal code still in force in 1906 it might be inflicted for the offences in the table given below, but not on offenders who were under twenty when they committed the offence. The annexed table indicates that the full sentence was sparingly executed. Under a Penal Code drafted in 1906, however, only two offences were made capital, viz. high treason against the person of the emperor and the graver cases of murder. The sentence is executed by hanging.

Belgium.—Under the Belgian Penal Code of 1867 the death penalty is retained for certain forms of high treason, and for assassination and parricide by poisoning. It may not be pronounced on a person under eighteen. The sentence is executed publicly by the guillotine. No execution seems to have taken place since 1863.

Denmark.—Sentence of death may be imposed for most forms of high treason, aggravated cases of murder, rape and piracy. It is executed publicly by the axe. Offenders under eighteen are not liable.

Finland.—In Finland the death penalty is alleged not to have been inflicted since 1824. It may be imposed for the assassination of the grand duke or grand duchess or the head of a friendly state, and wilful murder of other persons.

France.—Under the ancien régime in France, 115 crimes had become capital in 1789. The mode of execution varied, but in some cases it was effected by breaking on the wheel or burning, 281 and was coupled with mutilation. Under the Penal Code of 1810, as amended in or after 1832, even so late as 1871, thirty offences were capital, one being perjury against a prisoner resulting in his condemnation to death (art. 361). At present it may be imposed for wounding a public official with intent to murder (art. 233), assassination, parricide, poisoning, killing to commit a crime or escape from justice (arts. 302, 304). But juries freely exercise the power of acquitting in capital cases, or of defeating the capital sentence by finding extenuating circumstances in more than seven-eighths of the cases, which compels the court to reduce the punishment by one or more degrees, i.e. below the penalty of death. And in recent times the prerogative of mercy has been continually exercised by the president, even in gross cases where public opinion demanded the extreme penalty. The sentence is executed in public by the guillotine.

Germany.—In many of the states of Germany capital punishment had been abolished (Brunswick, Coburg, Nassau, Oldenburg in 1849; Saxe-Meiningen, Saxe-Weimar, 1862; Baden, 1863; Saxony, 1868). But it has been restored by the Imperial Criminal Code of 1872, in the case of attempts on the life of the emperor, or of the sovereign of any federal state in which the offender happens to be (s. 80), and for deliberate homicide (s. 211)—as opposed to intentional homicide without deliberation—and for certain treasonable acts committed when a state of siege has been proclaimed. The sentence is executed by beheading (s. 13).

Holland.—In Holland there have been no executions since 1860. Capital punishment (by hanging) was abolished in 1870, and was not reintroduced in the Penal Code of 1886.

Italy.—Capital punishment was abolished in Tuscany as far back as 1786, and from Italy has come the chief opposition to the death penalty, originated by Beccaria, and supported by many eminent jurists. Under the Penal Code of 1888 the death penalty was abrogated for all crimes, even for regicide. The cases of homicide in Italy are very numerous compared with those in England, amounting in 1905 to 105 per million as compared with 27 per million in the United Kingdom.

Japan.—The penalty of death is executed by hanging within a prison. It may be imposed for executing or contriving acts of violence against the mikado or certain of his family, and for seditious violence with the object of seizing the territory or subverting the government or laws of Japan, or conspiring with foreign powers to commence hostilities against Japan. It is inflicted for certain forms of homicide, substantially wilful murder in the first degree.

Norway.—Under Norwegian law, up to 1905, sentence of death might be passed for murder with premeditation, but the court might as an alternative decree penal servitude for life. Sentence of death had also to be passed in cases where a person under sentence of penal servitude for life committed murder or culpable homicide, or caused bodily injuries in circumstances warranting a sentence of penal servitude for life, or committed robbery or the graver forms of wilful fire-raising. The sentence was carried out by decapitation (see Beheading); but there had been no execution since 1876. The new Norwegian Code, which came into force on the 6th of January 1905, abolished capital punishment.

Portugal.—There has been considerable objection in Portugal to capital punishment, and it was abolished in 1867.

Rumania.—Capital punishment was abolished in 1864.

Russia.—In 1750, under the empress Elizabeth, capital punishment was abolished; but it was restored later and was freely inflicted, the sentence being executed by shooting, beheading or hanging. According to a Home Office Return in England in 1907 the death penalty is abolished, except in cases where the lives of the emperor, empress or heir to the throne are concerned.

Spain.—Under the Spanish Penal Code of 1870 the following crimes are capital:—inducing a foreign power to declare war against Spain, killing the sovereign, parricide and assassination. The method employed is execution in public by the garrote. But the death sentence is rarely imposed, the customary penalty for murder being penal servitude in chains for life, while a parricide is imprisoned in chains “in perpetuity until death.”

Sweden.—The severity of the law in Sweden was greatly mitigated so far back as 1777. Under the Penal Code of 1864 the penalty of death may be imposed for certain forms of treason, including attempts on the life of the sovereign or on the independence of Sweden, and for premeditated homicide (assassinat), and in certain cases for offences committed by persons under sentence of imprisonment for life. In 1901 a bill to abolish capital punishment was rejected by both houses of the Swedish parliament.

Switzerland.—Capital punishment was abolished in Switzerland in 1874 by Federal legislation; but in 1879, in consequence of a plebiscite, each canton was empowered to restore the death penalty for offences in its territory. The Federal government was unwilling to take this course, but was impelled to it by the fact that, between 1874 and 1879, cases of premeditated murder had considerably increased. Seven of the cantons out of twenty-two have exercised the power given to restore capital punishment. But there do not seem to have been any cases in which the death penalty has been inflicted; and on the assassination of the empress of Austria at Geneva in 1898 it was found that the laws of the canton did not permit the execution of the assassin. The canton of Zug imposes the lowest minimum penalty known, i.e. three years’ imprisonment for wilful homicide, the maximum being imprisonment for life.

United States of America.—Under the Federal laws sentence of death may be passed for treason against the United States and for piracy and for murder within the Federal jurisdiction. But for the most part the punishment of crime is regulated by the laws of the constituent states of the Union.

The death penalty was abolished in Michigan in 1846 except for treason, and wholly in Wisconsin in 1853. In Maine it was abolished in 1876, re-enacted in 1883, and again abolished in 1887. In Rhode Island it was abolished in 1852, but restored in 1882, only in case of murder committed by a person under sentence of imprisonment for life (Laws, 1896, c. 277, s. 2). In all the other states the death penalty may still be inflicted: in Alabama, Delaware, Georgia, Maryland, and West Virginia, for treason, murder, arson and rape; in Alaska, Arizona, Kansas, New Jersey, Mississippi, Montana, New York, North Dakota, Oregon, and South Dakota, for treason and murder; in Colorado, Idaho, Illinois, Iowa, Massachusetts, Minnesota, Nebraska, New Hampshire, New Mexico, Nevada, Ohio, Oklahoma, Pennsylvania, Utah and Wyoming, for murder only; in Kentucky and Virginia, for treason, murder and rape; in Vermont, for treason, murder and arson; in Indiana, for treason, murder, and for arson if death result; in California, for treason, murder and train-wrecking; in North Carolina, for murder, rape, arson and burglary; in Florida, Missouri, South Carolina, Tennessee and Texas, for murder and rape; in Arkansas and Louisiana, for treason, murder, rape, and administering poison or use of dangerous weapons with intent to murder. Louisiana is cited by Girardin (le droit de punir) as a state in which the death penalty was abolished in 1830. Under the influence of the eminent jurist, E. Livingston, who framed the state codes, the legislature certainly passed a resolution against capital punishment. But since as early as 1846 it has been there lawful, subject to a power given to the jury, to bring in a verdict of guilty, “but no capital punishment,” which had the effect of imposing a sentence of hard labour for life. In certain states the jury has, under local legislation, the right to award the sentence. The constitutionality of such legislation has been doubted, but has been recognized by the courts of Illinois and Iowa. Sentence of death is executed by hanging, except in seven of the states, where it is carried out by “electrocution” (q.v.).

With the mitigation of the law as to punishment, agitation against the theory of capital punishment has lost much of its force. But many European and American writers, and some English writers and associations, advocate the The question of abolition. total abolition of the death punishment. The ultimate argument of the opponents of capital punishment is that society has no right to take the life of any one of its members on 282 any ground. But they also object to capital punishment: (1) on religious grounds, because it may deprive the sinner of his full time for repentance; (2) on medical grounds, because homicide is usually if not always evidence of mental disease or irresponsibility; (3) on utilitarian grounds, because capital punishment is not really deterrent, and is actually inflicted in so few instances that criminals discount the risks of undergoing it; (4) on legal grounds, i.e. that the sentence being irrevocable and the evidence often circumstantial only, there is great risk of gross injustice in executing a person convicted of murder; (5) on moral grounds, that the punishment does not fit the case nor effect the reformation of the offender. It is to be noted that the English Children Act 1908 expressly forbids the pronouncing or recording the sentence of death against any person under the age of sixteen (s. 103).

The punishment is probably retained, partly from ingrained habit, partly from a sense of its appropriateness for certain crimes, but also that the ultima ratio may be available in cases of sufficient gravity to the commonweal. The apparent discrepancy between the number of trials and convictions for murder is not in England any evidence of hostility on the part of juries to capital punishment, which has on the whole lessened rather than increased since the middle of the 19th century. It is rarely if ever necessary in England, though common in America, to question the jurors as to their views on capital punishment. The reasons for the comparatively small number of convictions for murder seem to be: (1) that court and jury in a capital case lean in favorem vitae, and if the offence falls short of the full gravity of murder, conviction for manslaughter only results; (2) that in the absence of a statutory classification of the degrees of murder, the prerogative of mercy is exercised in cases falling short of the highest degree of gravity recognized by lawyers and by public opinion; (3) that where the conviction rests on circumstantial evidence the sentence is not executed unless the circumstantial evidence is conclusive; (4) that charges of infanticide against the mothers of illegitimate children are treated mercifully by judge and jury, and usually terminate in acquittal, or in a conviction of concealment of birth; (5) that many persons tried as murderers are obviously insane; (6) that coroners’ juries are somewhat recklessly free in returning inquisitions of murder without any evidence which would warrant the conviction of the person accused.

The medical doctrine, and that of Lombroso with respect to criminal atavism and irresponsibility, have probably tended to incline the public mind in favour of capital punishment, and Sir James Stephen and other eminent jurists have even been thereby tempted to advocate the execution of habitual criminals. It certainly seems strange that the community should feel bound carefully to preserve and tend a class of dangerous lunatics, and to give them, as Charles Kingsley says, “the finest air in England and the right to kill two gaolers a week.”

The whole question of capital punishment in the United Kingdom was considered by a royal commission appointed in 1864, which reported in 1866 (Parl. Pap., 1866, 10,438). The commission took the opinions of all the judges of the supreme courts in the United Kingdom and of many other eminent persons, and collected the laws of other countries so far as this was ascertainable. The commissioners differed on the question of the expediency of abolishing or retaining capital punishment, and did not report thereon. But they recommended: (1) that it should be restricted throughout the United Kingdom to high treason and murder; (2) alteration of the law of homicide so as to classify homicides according to their gravity, and to confine capital punishment to murder in the first degree; (3) modification of the law as to child murder so as to punish certain cases of infanticide as misdemeanours; (4) authorizing judges to direct sentence of death to be recorded; (5) the abolition—since carried out—of public executions.

CAPITO (or Köpfel), WOLFGANG [Fabricius] (1478-1541), German reformer, was born of humble parentage at Hagenau in Alsace. He was educated for the medical profession, but also studied law, and applied himself so earnestly to theology that he received the doctorate in that faculty also, and, having joined the Benedictines, taught for some time at Freiburg. He acted for three years as pastor in Bruchsal, and was then called to the cathedral church of Basel (1515). Here he made the acquaintance of Zwingli and began to correspond with Luther. In 1519 he removed to Mainz at the request of Albrecht, archbishop of that city, who soon made him his chancellor. In 1523 he settled at Strassburg, where he remained till his death in November 1541. He had found it increasingly difficult to reconcile the new religion with the old, and from 1524 was one of the leaders of the reformed faith in Strassburg. He took a prominent part in the earlier ecclesiastical transactions of the 16th century, was present at the second conference of Zurich and at the conference of Marburg, and along with Martin Bucer drew up the Confessio Tetrapolitana. Capito was always more concerned for the “unity of the spirit” than for dogmatic formularies, and from his endeavours to conciliate the Lutheran and Zwinglian parties in regard to the sacraments, he seems to have incurred the suspicions of his own friends; while from his intimacy with Martin Cellarius and other divines of the Socinian school he drew on himself the charge of Arianism. His principal works were:—Institutionum Hebraicarum libri duo; Enarrationes in Habacuc et Hoseam Prophetas; a life of Oecolampadius and an account of the synod of Berne (1532).

CAPITULARY (Med. Lat. capitularium), a series of legislative or administrative acts emanating from the Merovingian and Carolingian kings, so called as being divided into sections or chapters (capitula). With regard to these capitularies two questions arise: (1) as to the means by which they have been handed down to us; (2) as to their true character and scope.

(1) As soon as the capitulary was composed, it was sent to the various functionaries of the Frankish empire, archbishops, bishops, missi and counts, a copy being kept by the chancellor in the archives of the palace. At the present day we do not possess a single capitulary in its original form: but very frequently copies of these isolated capitularies were included in various scattered manuscripts, among pieces of a very different nature, ecclesiastical or secular. We find, therefore, a fair number of them in books which go back as far as the 9th or 10th centuries. In recent editions in the case of each capitulary it is carefully indicated from what manuscripts it has been collated.

These capitularies make provisions of a most varied nature; it was therefore found necessary at quite an early date to classify them into chapters according to the subject. In 827 Ansegisus, abbot of St Wandrille at Fontenelle, made such a collection. He embodied them in four books: one of the ecclesiastical capitularies of Charlemagne, one of the ecclesiastical capitularies of Louis the Pious, one of the secular capitularies of Charlemagne, and one of the secular capitularies of Louis, bringing together similar provisions and suppressing duplicates. This collection soon gained an official authority, and after 829 Louis the Pious refers to it, citing book and section.

After 827 new capitularies were naturally promulgated, and before 858 there appeared a second collection in three books, by an author calling himself Benedictus Levita. His aim was, he said, to complete the work of Ansegisus, and bring it up to date by continuing it from 827 to his own day; but the author has not only borrowed prescriptions from the capitularies; he has introduced other documents into his collection, fragments of Roman laws, canons of the councils and especially spurious provisions very similar in character to those of the same date found in the False Decretals. His contemporaries did not notice these spurious documents, but accepted the whole collection as 283 authentic, and incorporated the four books of Ansegisus and the three of Benedictus Levita into a single collection in seven books. The serious historian of to-day, however, is careful not to use books v., vi. and vii. for purposes of reference.

Early editors chose to republish this collection of Ansegisus and Benedictus as they found it. It was a distinguished French scholar, Étienne Baluze, who led the way to a fresh classification. In 1677 he brought out the Capitularia regum francorum, in two folio volumes, in which he published first the capitularies of the Merovingian kings, then those of Pippin, of Charles and of Louis the Pious, which he had found complete in various manuscripts. After the date of 840, he published as supplements the unreliable collection of Ansegisus and Benedictus Levita, with the warning that the latter was quite untrustworthy. He then gave the capitularies of Charles the Bald, and of other Carolingian kings, either contemporaries or successors of Charles, which he had discovered in various places. A second edition of Baluze was published in 1780 in 2 volumes folio by Pierre de Chiniac.

The edition of the Capitularies made in 1835 by George Pertz, in the Monumenta Germaniae (folio edition, vol. i., of the Leges) was not much advance on that of Baluze. A fresh revision was required, and the editors of the Monumenta decided to reissue it in their quarto series, entrusting the work to Dr Alfred Boretius. In 1883 Boretius published his first volume, containing all the detached capitularies up to 827, together with various appendices bearing on them, and the collection of Ansegisus. Boretius, whose health had been ruined by overwork, was unable to finish his work; it was continued by Victor Krause, who collected in vol. ii. the scattered capitularies of a date posterior to 828. Karl Zeumer and Albrecht Werminghoff drew up a detailed index of both volumes, in which all the essential words are noted. A third volume, prepared by Emil Seckel, was to include the collection of Benedictus Levita.

(2) Among the capitularies are to be found documents of a very varied kind. Boretius has divided them into several classes:—

(a) The Capitula legibus addenda.—These are additions made by the king of the Franks to the barbarian laws promulgated under the Merovingians, the Salic law, the Ripuarian or the Bavarian. These capitularies have the same weight as the law which they complete; they are particular in their application, applying, that is to say, only to the men subject to that law. Like the laws, they consist chiefly of scales of compensation, rules of procedure and points of civil law. They were solemnly promulgated in the local assemblies where the consent of the people was asked. Charlemagne and Louis the Pious seem to have made efforts to bring the other laws into harmony with the Salic law. It is also to be noted that by certain of the capitularies of this class, the king adds provisions affecting, not only a single law, but all the laws in use throughout the kingdom.

(b) The Capitula ecclesiastica.—These capitularies were elaborated in the councils of the bishops; the kings of the Franks sanctioned the canon of the councils, and made them obligatory on all the Christians in the kingdom.

(c) The Capitula per se scribenda.—These embodied political decrees which all subjects of the kingdom were bound to observe. They often bore the name of edictum or of constitutio, and the provisions made in them were permanent. These capitularies were generally elaborated by the king of the Franks in the autumn assemblies or in the committees of the spring assemblies. Frequently we have only the proposition made by the king to the committee, capitula tractanda cum comitibus, episcopis, et abbatibus, and not the final form which was adopted.

(d) The Capitula missorum, which are the instructions given by Charlemagne and his successors to the missi sent into the various parts of the empire. They are sometimes drawn up in common for all the missi of a certain year—capitula missorum generalia; sometimes for the missi sent only on a given circuit—capitula missorum specialia. These instructions sometimes hold good only for the circuit of the missus; they have no general application and are merely temporary.

(e) With the capitularies have been incorporated various documents; for instance, the rules to be observed in administering the king’s private domain (the celebrated capitulary de villis, which is doubtless a collection of the instructions sent at various times to the agents of these domains); the partitions of the kingdom among the king’s sons, as, the Divisio regnorum of 806, or the Ordinatio imperii of 817; the oaths of peace and brotherhood which were taken on various occasions by the sons of Louis the Pious, &c.

The merit of clearly establishing these distinctions belongs to Boretius. He has doubtless exaggerated the difference between the Capitula missorum and the Capitula per se scribenda; among the first are to be found provisions of a general and permanent nature, and among the second temporary measures are often included. But the idea of Boretius is none the less fruitful. In the capitularies there are usually permanent provisions and temporary provisions intermingled; and the observation of this fact has made it possible more clearly to understand certain institutions of Charlemagne, e.g. military service.

After the reign of Louis the Pious the capitularies became long and diffuse. Soon, from the 10th century onwards, no provision of general application emanates from the kings. Henceforth the kings only regulated private interests by charters; it was not until the reign of Philip Augustus that general provisions again appeared; but when they did so, they bore the name of ordinances (ordonnances).

There were also capitularies of the Lombards. These capitularies formed a continuation of the Lombard laws, and are printed as an appendix to these laws by Boretius in the folio edition of the Monumenta Germaniae, Leges, vol. iv.

CAPITULATION (Lat. capitulum, a little head or division; capitulare, to treat upon terms), an agreement in time of war for the surrender to a hostile armed force of a particular body of troops, a town or a territory. It is an ordinary incident of war, and therefore no previous instructions from the captor’s government are required before finally settling the conditions of capitulation. The most usual of such conditions are freedom of religion and security of private property on the one hand, and a promise not to bear arms within a certain period on the other. Such agreements may be rashly concluded with an inferior officer, on whose authority the enemy are not in the actual position of the war entitled to place reliance. When an agreement is made by an officer who has not the proper authority or who has exceeded the limits of his authority, it is termed a sponsion, and, to be binding, must be confirmed by express or tacit ratification. Article 35 of the Hague Convention (1899) on the laws and the customs of war lays down that “capitulations agreed on between the contracting parties must be in accordance with the rules of military honour. When once settled they must be observed by both the parties.”

In another sense, capitulation is the name given to an arrangement by which foreigners are withdrawn, for most civil and criminal purposes, from the jurisdiction of the state making the capitulation. Thus in Turkey arrangements termed capitulations (q.v.), and treaties confirmatory of them, have been made between the Porte and other states by which foreigners resident in Turkey are subject to the laws of their respective countries. The term is also applied by French writers to the oath which on his election the Holy Roman emperor used to make to the college of electors; this related chiefly to such matters as regalian rights, appeals from local jurisdictions, the rights of the pope, &c.

CAPITULATIONS (from Lat. caput, or its Low-Latin diminutive capitulum, as indicating the form in which these acts were set down in “chapters”; the Gr. equivalent cephaleosis, kephalaiosis, is occasionally used in works of the 17th century), treaties granted by a state and conferring the privilege of extra-territorial jurisdiction within its boundaries on the subjects of another state. Thus, in the 9th century, the caliph Harun-al-Rashid engaged to grant guarantees and commercial facilities to such 284 Franks, subjects of the emperor Charlemagne, as should visit the East with the authorization of their emperor. After the break-up of the Frank empire, similar concessions were made to some of the practically independent Italian city states that grew up on its ruins. Thus, in 1098, the prince of Antioch granted a charter of this nature to the city of Genoa; the king of Jerusalem extended the same privilege to Venice in 1123 and to Marseilles in 1136. Salah-ud-din (Saladin), sultan of Babylon (Cairo), granted a charter to the town of Pisa in 1173. The Byzantine emperors followed this example, and Genoa, Pisa and Venice all obtained capitulations. The explanation of the practice is to be found in the fact that the sovereignty of the state was held in those ages to apply only to its subjects; foreigners were excluded from its rights and obligations. The privilege of citizenship was considered too precious to be extended to the alien, who was long practically an outlaw. But when the numbers, wealth and power of foreigners residing within the state became too great, it was found to be politic to subject them to some law, and it was held that this law should be their own. When the Turkish rule was substituted for that of the Byzantine emperors, the system already in existence was continued; the various non-Moslem peoples were allowed their semi-autonomy in matters affecting their personal status, and the Genoese of Galata were confirmed in their privileges. But the first capitulation concluded with a foreign state was that of 1535 granted to the French. Lest it should be imagined that this was a concession wrested by the victorious Christian monarch from the decadent Turk, it should be borne in mind that Turkey was then at the height of her power, and that Francis I. had shortly before sustained a disastrous defeat at Pavia. His only hope of assistance lay in Suleiman I., whose attack on Vienna had been checked by the victorious Charles V. The appeal to Suleiman on the ground of the common interest of France and Turkey in overcoming Charles V.’s overweening power was successful; the secret mission of Frangipani, an unofficial envoy who could be disowned in case of failure, paved the way for De la Forest’s embassy in 1534, and in 1536 the capitulations were signed.1 They amounted to a treaty of commerce and a treaty allowing the establishment of Frenchmen in Turkey and fixing the jurisdiction to be exercised over them: individual and religious liberty is guaranteed to them, the king of France is empowered to appoint consuls in Turkey, the consuls are recognized as competent to judge the civil and criminal affairs of French subjects in Turkey according to French law, and the consuls may appeal to the officers of the sultan for their aid in the execution of their sentences. This, the first of the capitulations, is practically the prototype of its successors. Five years later, similar capitulations were concluded with Venice. The capitulations were at first held to be in force only during the lifetime of the sultan by whom they were granted; thus in 1569 Sultan Selim II. renewed the French capitulations granted by his predecessor. In 1583 England obtained her first capitulation, until which time France had been the official protector of all Europeans established in Turkey. Later on, England claimed to protect the subjects of other nations, a claim which is rejected in the French capitulations of 1597, 1604 and 1607, the last-named of which explicitly lays down that the subjects of all nations not represented at Constantinople by an ambassador shall be under French protection. In 1613 Holland obtained her first capitulation, with the assistance of the French ambassador, anxious to help a commercial rival of England. In 1673 the French, represented by the marquis de Nointel, succeeded in obtaining the renewal of the capitulations which, for various reasons, had remained unconfirmed since 1607. Louis XIV. had been anxious to secure the protectorate of all Catholics in Turkey, but was obliged to content himself with the recognition of his right to protect all Latins of non-Turkish nationality; his claims for the restoration to the Catholics of the Holy Places usurped by the Greeks was also rejected, the sultan only undertaking to promise to restore their churches to the Jesuit Capuchins. An important commercial gain was the reduction of the import duties from 5 to 3%; and all suits the value of which exceeded 4000 aspres in which French subjects sued, or were sued by, an Ottoman subject, were to be heard not by the ordinary tribunals but at the Porte itself. Later, France’s friendship secured for Turkey a successful negotiation of the peace of Belgrade in 1739, and the result was the capitulation of 1740; this is no longer limited in duration to the sultan’s lifetime but is made perpetual, and, moreover, declares that it cannot be modified without the assent of the French. It conferred on the French ambassador precedence over his colleagues. Austria had obtained capitulations in 1718, modified in 1784; Russia secured similar privileges in 1784. In the course of the 18th century nearly every European power had obtained these, and such newly-established countries as the United States of America, Belgium and Greece followed in the 19th century.

The chief privileges granted under the capitulations to foreigners resident in Turkey are the following: liberty of residence, inviolability of domicile, liberty to travel by land and sea, freedom of commerce, freedom of religion, immunity from local jurisdiction save under certain safeguards, exclusive extra-territorial jurisdiction over foreigners of the same nationality, and competence of the forum of the defendant in cases in which two foreigners are concerned (though the Sublime Porte has long claimed to exercise jurisdiction in criminal cases in which two foreigners of different nationality are concerned—the capitulations are silent on the point and the claim is resisted by the powers).

The same system has been followed by such countries as Persia, China, Japan and Siam.

The practical result of the capitulations in Turkey is to form each separate foreign colony into a sort of imperium in imperio, and to hamper the local jurisdiction very considerably. As the state granting the capitulations progresses in civilization it chafes under these restraints in its sovereignty. Turkey’s former vassals, Rumania and Servia, though theoretically bound to respect the capitulations so long as they formed part of Turkey, had practically abrogated them long before securing their independence through the treaty of Berlin in 1878. The same may be said of Bulgaria. Japan was liberated from the burden of the capitulations some years ago.

The extra-territorial jurisdiction exercised by the foreign powers over their subjects in Turkey and other countries where capitulations exist is regulated by special legislative enactments; in the case of the United Kingdom by orders in council.

In Turkey the capitulations are practically the only treaties in force with the powers, since the expiration about 1889 of the commercial treaties concluded in 1861-1862. As they all contain the “most-favoured nation” clause, the privileges in any one apply to all the powers, though not always claimed. Thus America and Belgium claim under their treaties with Turkey the right to try all their subjects, even if accused of offences against Ottoman subjects—a claim recently made by Belgium in the case of the Belgian subject Joris, accused of participation in the bomb outrage of 1905 at Yildiz. One peculiar privilege granted in the capitulations of 1675 (Art. 74) authorizes the king of England to buy in Turkey with his own money two cargoes of figs and raisins, in fertile and abundant years and not in times of dearth or scarcity, and provides that after a duty of 3% has been paid thereon no obstacle or hindrance shall be given thereto.

CAPIZ, a town and the capital of the province of Capiz, Panay, Philippine Islands, on the Capiz or Panay river, about 4 m. from its mouth on the N. coast. Pop. (1903) 18,525. Capiz has a large and beautiful Roman Catholic church (of stone), a Protestant church (with a hospital) and good government buildings, and is the seat of the provincial high school. Alcohol of a superior quality is manufactured in large quantities from the fermented juice of the nipa palm, which grows plentifully in the neighbouring swamps. Fishing and the weaving of fabrics of cotton, hemp and pineapple fibre are important industries. Rice and sugar are raised in abundance. Tobacco, Indian corn 285 and cacao are produced to a limited extent; and rice, alcohol, sugar and copra are exported. Coasting vessels ascend the river to the town. The language is Visayan.

CAPMANY Y MONTPALAU, ANTONIO DE (1742-1813), Spanish polygraph, was born at Barcelona on the 24th of November 1742. He retired from the army in 1770, and was subsequently elected secretary of the Royal Academy of History at Madrid. His principal works are—Memorias históricas sobre la marina, commercio, y artes de la antigua ciudad de Barcelona (4 vols. 1779-1792); Teatro histórico-critico de la elocuencia Española (1786); Filiosofía de la elocuencia (1776), and Cuestiones críticas sobre varias puntos de historia ecónomica, política, y militar (1807). Capmany died at Barcelona on the 14th of November 1813. His monograph on the history of his birthplace still preserves much of its original value.

CAPO D’ISTRIA, GIOVANNI ANTONIO [Joannes],1 Count (1776-1831), Russian statesman and president of the Greek republic, was born at Corfu on the 11th of February 1776. He belonged to an ancient Corfiot family which had immigrated from Istria in 1373, the title of count being granted to it by Charles Emmanuel, duke of Savoy, in 1689. The father of Giovanni, Antonio Maria Capo d’Istria, was a man of considerable importance in the island, a stiff aristocrat of the old school, who in 1798, after the treaty of Campo Formio had placed the Ionian Islands under French rule, was imprisoned for his opposition to the new regime, his release next year being the earliest triumph of his son’s diplomacy. On the establishment in 1800, under Turkish suzerainty, of the septinsular republic—a settlement negotiated at Constantinople by the elder Capo d’Istria—Giovanni, who had meanwhile studied medicine at Padua, entered the government service as secretary to the legislative council, and in one capacity or another exercised for the next seven years a determining voice in the affairs of the republic. At the beginning of 1807 he was appointed “extraordinary military governor” to organize the defence of Santa Maura against Ali Pasha of Iannina, an enterprise which brought him into contact with Theodores Kolokotrones and other future chiefs of the war of Greek independence, and awoke in him that wider Hellenic patriotism which was so largely to influence his career.

Throughout the period of his official connexion with the Ionian government, Capo d’Istria had been a consistent upholder of Russian influence in the islands; and when the treaty of Tilsit (1807) dashed his hopes by handing over the Ionian republic to Napoleon, he did not relinquish his belief in Russia as the most reliable ally of the Greek cause. He accordingly refused the offers made to him by the French government, and accepted the invitation of the Russian chancellor Romanzov to enter the tsar’s service. He went to St Petersburg in 1809, and was appointed to the honorary post of attaché to the foreign office, but it was not till two years after, in 1811, that he was actually employed in diplomatic work as attaché to Baron Stackelberg, the Russian ambassador at Vienna. His knowledge of the near East was here of great service, and in the following year he was attached, as chief of his diplomatic bureau, to Admiral Chichagov, on his mission to the Danubian principalities to stir up trouble in the Balkan peninsula as a diversion on the flank of Austria, and to attempt to supplement the treaty of Bucharest by an offensive and defensive alliance with the Ottoman empire. The Moscow campaign of 1812 intervened; Chichagov was disgraced in consequence of his failure to destroy Napoleon at the passage of the Beresina; but Capo d’Istria was not involved, was made a councillor of state and continued in his diplomatic functions. During the campaign of 1813 he was attached to the staff of Barclay de Tolly and was present at the battles of Lützen, Bautzen, Dresden and Leipzig. With the advance of the allies he was sent to Switzerland to secure the withdrawal of the republic from the French alliance. Here, in spite of his instructions to guarantee the neutrality of Switzerland, he signed on his own responsibility the proclamation issued by Prince Schwarzenberg, stating the intention of the allied troops to march through the country. His motive was to prevent any appearance of disagreement among the allies. The emperor Alexander, to whom he hastened to make an explanation in person, endorsed his action.

Capo d’Istria was present with the allies in Paris, and after the signing of the first peace of Paris he was rewarded by the tsar with the order of St Vladimir and his full confidence. At the congress of Vienna his influence was conspicuous; he represented the tsar on the Swiss committee, was associated with Rasumovsky in negotiating the tangled Polish and Saxon questions, and was the Russian plenipotentiary in the discussions with the Baron vom Stein on the affairs of Germany. His Mémoire sur l’empire germanique, of the 9th of February 1815, presented to the tsar, was based on the policy of keeping Germany weak in order to secure Russian preponderance in its councils. It was perhaps from a similar motive that, after the Waterloo campaign, he strenuously opposed the proposals for the dismemberment of France. It was on his advice that the duc de Richelieu persuaded Louis XVIII. to write the autograph letter in which he declared his intention of resigning rather than submit to any diminution of the territories handed down to him by his ancestors.2 The treaty of the 20th of November 1815, which formed for years the basis of the effective concert of Europe, was also largely his work.

On the 26th of September 1815, after the proclamation of the Holy Alliance at the great review on the plain of Vertus, Capo d’Istria was named a secretary of state. On his return to St Petersburg, he shared the ministry of foreign affairs with Count Nesselrode, though the latter as senior signed all documents. Capo d’Istria, however, had sole charge of the newly acquired province of Bessarabia, which he governed conspicuously well. In 1818 he attended the emperor Alexander at the congress of Aix-la-Chapelle, and in the following year obtained leave to visit his home. He travelled by way of Venice, Rome and Naples, his progress exciting the liveliest apprehensions of the powers, notably of Austria. The “Jacobin” pose of the tsar was notorious, his all-embracing ambition hardly less so; and Russian travellers in Italy, notably the emperor’s former tutor, César de Laharpe, were little careful in the expression of their sympathy for the ideals of the Carbonari. In Metternich’s eyes Capo d’Istria, “the coryphaeus of liberalism,” was responsible for the tsar’s vagaries, the fount of all the ills of which the times were sick; and, for all the count’s diplomatic reticence, the Austrian spies who dogged his footsteps earned their salaries by reporting sayings that set the reactionary courts in a flutter. For Metternich the overthrow of Capo d’Istria’s influence became a necessity of political salvation. At Corfu Capo d’Istria became the repository of all the grievances of his countrymen against the robust administration of Sir Thomas Maitland. At the congress of Vienna the count had supported the British protectorate over the Ionian Islands, the advantages of which from the point of view of trade and security were obvious; but the drastic methods of “King Tom’s” government, symbolized by a gallows for pirates and other evil-doers in every popular gathering place, offended his local patriotism. He submitted a memorandum on the subject to the tsar, and before returning to Russia travelled via Paris to England to lay the grievances of the Ionians before the British government. His reception was a cold one, mainly due to his own disingenuousness, for he refused to show British ministers the memorandum which he had already submitted to the Russian emperor, on the ground that it was intended only for his own private use. The whole thing seemed, rightly or wrongly, an excuse for the intervention of Russia in affairs which were by treaty wholly British.

On his return to St Petersburg in the autumn of 1819, Capo d’Istria resumed his influence in the intimate counsels of the tsar. The murder of the Russian agent, Kotzebue, in March, had shaken but not destroyed Alexander’s liberalism, and it was Capo d’Istria who drew up the emperor’s protest against the Carlsbad decrees and the declaration of his adherence to constitutional views (see Alexander I.). In October 1820 Capo 286 d’Istria accompanied the tsar to the congress at Troppau. The events of the year—the murder of the due de Berry in March, the Revolutions in Spain and in Naples—had produced their effect. Alexander was, in Metternich’s exultant language, “a changed man,” and Capo d’Istria apparently shared his conversion to reactionary principles. The Austrian chancellor now put forth all his powers to bring Alexander under his own influence, and to overthrow Capo d’Istria, whom he despised, distrusted and feared. In 1821 Alexander Ypsilanti’s misguided raid into the Danubian principalities gave him his opportunity. The news reached the tsar at the congress of Laibach, and to Capo d’Istria was entrusted the task of writing the letter to Ypsilanti in which the tsar repudiated his claim, publicly proclaimed that he had the sympathy and support of Russia. For a while the position of Capo d’Istria was saved; but it was known that he had been approached by the agent of the Greek Hetairia before Ypsilanti, and that he had encouraged Ypsilanti to take up the ill-fated adventure which he himself had refused; he was hated at the Russian court as an upstart Greek, and Metternich was never weary of impressing on all and sundry that he was “using Russian policy for Greek ends.” At last nothing but long habit and native loyalty to those who had served him well, prevented Alexander from parting with a minister who had ceased to possess his confidence. Capo d’Istria, anticipating his dismissal, resigned on the eve of the tsar’s departure for the congress of Verona (1822), and retired into private life at Geneva.

On the 11th of April 1827, the Greek national assembly at Troezene elected Capo d’Istria president of the republic. The vote was a triumph for the Russian faction, for the count, even after his fall, had not lost the personal regard of the emperor Alexander, nor ceased to consider himself a Russian official. He accepted the offer, but was in no hurry to take up the thankless task. In July he visited the emperor Nicholas I. at Tsarskoye Selo, receiving permission to proceed and instructions as to the policy he should adopt, and he next made a tour of the courts of Europe in search of moral and material support. The news of the battle of Navarino (20th of October 1827) hastened his arrival; the British frigate “Warspite” was placed at his disposal to carry him to Greece, and on the 19th of January 1828 he landed at Nauplia.

Capo d’Istria’s rule in Greece had to contend against immense difficulties—the utter poverty of the treasury, the barbarism of the people but recently emancipated, the continued presence of Ibrahim Pasha, with an unbroken army, in the south of the Morea. His strength lay in his experience of affairs and in the support of Russia; but he was by inheritance an aristocrat and by training an official, lacking in broad human sympathy, and therefore little fitted to deal with the wild and democratic elements of the society it was his task to control. The Greeks could understand the international status given to them by his presidency, and for a while the enthusiasm evoked by his arrival made him master of the situation. He thoroughly represented Greek sentiment, too, in his refusal to accept the narrow limits which the powers, in successive protocols, sought to impose on the new state (see Greece). But the Russian administrative system by which he sought to restrain the native turbulence was bound in the end to be fatal to him. The wild chiefs of the revolution won over at first by their inclusion in his government, were offended by his European airs and Russian uniform, and alienated by his preference for the educated Greeks of the Phanar and of Corfu, his promotion of his brothers Viaro and Agostino to high commands causing special offence. Dissatisfaction ended in open rebellion; the islands revolted; Capo d’Istria called in the aid of the Russian admiral; and Miaoulis, the hero of the Greek war at sea, blew up the warships under his command to prevent their falling into the hands of the government. On land, so far as the president was concerned, the climax was reached with the attempt to coerce the Mavromichales of the Maina, the bravest and most turbulent of the mountain clans, whose chief Petros Mavromichales, commonly known as Petrobey, had played a leading part in the War of Independence. The result was an insurrection in the Maina (Easter, 1830), and the imprisonment of those of the Mavromichales, including Petrobey, who happened to be in the power of the government. At the news of their chieftain’s imprisonment the Mainots, who had for a while been pacified, once more flew to arms and threatened to march on Nauplia; but negotiations were opened, and on the advice of the Russian minister Petrobey consented to make his submission to the president. Unhappily, when he was brought under guard to the appointed interview, Capo d’Istria, in a moment of irritation and weariness, refused to see him. Maddened with rage at this insult from a man who had not struck a blow for Greece, the proud old chief, on his way back to prison, called out to two of his kinsmen, his son George and his brother Constantino, “You see how I fare,” and passed on. According to the code of the Maina this was a command to take revenge. Next day, the 9th of October 1831, the two placed themselves at the door of the church where Capo d’Istria was accustomed to worship. As he passed in Constantine shot him down, and as he fell George thrust a dagger into his heart.

CAPODISTRIA, a town and seaport of Austria, in Istria, 15 m. S.W. of Trieste by rail. Pop. (1900) 10,711, mostly Italians. It is situated on a small island, which occupies the end of a large bay in the Gulf of Trieste, and which is connected with the mainland by a causeway half a mile in length. Capodistria is an old town with small streets, and has preserved remarkably well its Italian, almost its Venetian character. The most noteworthy buildings are the cathedral, the town-hall and the Loggia or the old law-court, all situated in the principal square. In addition to the extraction of salt from the sea in the extensive salt works near the town, fishing and shipbuilding are the other principal occupations of the population. Trade is chiefly in sea-salt, wine and oil. Capodistria is usually identified with the town of Aegida, mentioned by Pliny, which appears by an inscription to have afterwards received (in the 6th century) the name of Justinopolis from Justin II. When at the beginning of the 13th century Istria fell into the hands of the patriarchs of Aquileia, they made this town the capital of the whole province. Thence it acquired its actual name, which means the capital of Istria. It was captured by the Venetians in 1279, and passed into Austrian possession in 1797.

CAPONIER (from the Fr. caponnière, properly a capon-cote or house), in fortification, a work constructed in the ditch of a fort. Its fire (musketry, machine-guns, case shot, &c.) sweeps the bottom of the ditch and prevents an enemy from establishing himself in it. The term is used in a military sense as early as in the late 17th century. In various bastioned systems of fortification a caponier served merely as a covered means of access to outworks, the bastion trace providing for the defence of the ditch by fire from the main parapet.

CAPPADOCIA, in ancient geography, an extensive inland district of Asia Minor. In the time of Herodotus the Cappadocians occupied the whole region from Mount Taurus to the Euxine. That author tells us that the name of the Cappadocians (Katpatouka) was applied to them by the Persians, while they were termed by the Greeks “Syrians,” or “White Syrians” (Leucosyri). Under the later kings of the Persian empire the 287 were divided into two satrapies or governments, the one comprising the central and inland portion, to which the name of Cappadocia continued to be applied by Greek geographers, while the other was called Cappadocia κατὰ Πόντον, or simply Pontus (q.v.). This division had already come about before the time of Xenophon. As after the fall of the Persian government the two provinces continued to be separate, the distinction was perpetuated, and the name Cappadocia came to be restricted to the inland province (sometimes called Great Cappadocia), which alone will be considered in the present article.

Cappadocia, in this sense, was bounded S. by the chain of Mount Taurus, E. by the Euphrates, N. by Pontus, and W. vaguely by the great central salt “Desert” (Axylon). But it is impossible to define its limits with accuracy. Strabo, the only ancient author who gives any circumstantial account of the country, greatly exaggerated its dimensions; it was in reality about 250 m. in length by less than 150 in breadth. With the exception of a narrow strip of the district called Melitene, on the east, which forms part of the valley of the Euphrates, the whole of this region is a high upland tract, attaining to more than 3000 ft., and constituting the most elevated portion of the great tableland of Asia Minor (q.v.). The western parts of the province, where it adjoins Lycaonia, extending thence to the foot of Mount Taurus, are open treeless plains, affording pasture in modern as in ancient times to numerous flocks of sheep, but almost wholly desolate. But out of the midst of this great upland level rise detached groups or masses of mountains, mostly of volcanic origin, of which the loftiest are Mount Argaeus (still called by the Turks Erjish Dagh), (13,100 ft.), and Hassan Dagh to the south-west (8000 ft.).

The eastern portion of the province is of a more varied and broken character, being traversed by the mountain system called by the Greeks Anti-Taurus. Between these mountains and the southern chain of Taurus, properly so called, lies the region called in ancient times Cataonia, occupying an upland plain surrounded by mountains. This district in the time of Strabo formed a portion of Cappadocia and was completely assimilated; but earlier writers and the Persian military system regarded the Cataonians as a distinct people.

Cappadocia contained the sources of the Sarus and Pyramus rivers with their higher affluents, and also the middle course of the Halys (see Asia Minor), and the whole course of the tributary of Euphrates now called Tokhma Su. But as no one of these rivers was navigable or served to fertilize the lands along its torrential course, none has much importance in the history of the province.

The kingdom of Cappadocia, which was still in existence in the time of Strabo, as a nominally independent state, was divided, according to that geographer, into ten districts. Of these Cataonia has been described; the adjoining district of Melitene, which did not originally form part of Cappadocia at all, but was annexed to it by Ariarathes I., was a fertile tract adjoining the Euphrates; its chief town retains the name of Malatia. Cilicia was the name given to the district in which Caesarea, the capital of the whole country was situated, and in which rose the conspicuous Mount Argaeus. Tyanitis, the region of which Tyana was the capital, was a level tract in the extreme south, extending to the foot of Mount Taurus. Garsauritis appears to have comprised the western or south-western districts adjoining Lycaonia; its chief town was Archelais. Laviansene or Laviniane was the country south and south-east of Sivas, through which ran the road from Sebastea to Caesarea: Sargarausene lay south of the above, and included Uzun Yaila and the upper basin of the Tokhma Su; Saravene lay west of Laviansene and included the modern district of Ak Dagh; Chamanene lay west again of the above along the middle course of the Halys: Morimene was the north-western district extending along the edge of the central desert as far south as Melegob.

The only two cities of Cappadocia considered by Strabo to deserve that appellation were Mazaca, the capital of the kingdom under its native monarchs (see Caesarea-Mazaca); and Tyana, not far from the foot of the Taurus, the site of which is marked by a great mound at a place called Kiz (or Ekuz) Hissar, about 12 m. south-west of Nigdeh. Archelais, founded by Archelaus, the last king of the country, subsequently became a Roman colony, and a place of some importance. It is now Akserai.

Several localities in the Cappadocian country were the sites of famous temples. Among these the most celebrated were those of Comana (q.v.) and Venasa in Morimene, where a male god was served by over 3000 hieroduli. The local sanctity of Venasa has been perpetuated by the Moslem veneration for Haji Bektash, the founder of the order of dervishes to which the Janissaries used in great part to belong. Cappadocia was remarkable for the number of its slaves, which constituted the principal wealth of its monarchs. Large numbers were sent to Rome but did not enjoy a good reputation. The Cappadocian peasants are still in the habit of taking service in the West of the peninsula and only returning to their homes after long absences; their labour is now much valued by employers, as they are a strong sober folk. The province was celebrated for its horses, as well as for its vast flocks of sheep; but from its elevation above the sea, and the coldness of its climate, it could never have been rich and fertile.

History.—Nothing is known of the history of Cappadocia before it became subject to the Persian empire, except that the country was the home of a great “Hittite” power centred at Boghaz-Keui (see Pteria), which has left monuments at many places, e.g. Nevsheher, Fraktin, Gorun, Malatia, various points about Albistan and Derendeh, Bulgur Maden, Andaval and Tyana. Possibly the princes of the last named city were independent. With the decline of the Syro-Cappadocians after their defeat by Croesus, Cappadocia was left in the power of a sort of feudal aristocracy, dwelling in strong castles and keeping the peasants in a servile condition, which later made them apt for foreign slavery. It was included in the third Persian satrapy in the division established by Darius, but long continued to be governed by rulers of its own, none apparently supreme over the whole country and all more or less tributary to the Great King. Thoroughly subdued at last by the satrap Datames, Cappadocia recovered independence under a single ruler, Ariarathes (hence called Ariarathes I.), who was a contemporary of Alexander the Great, and maintained himself on the throne of Cappadocia after the fall of the Persian monarchy.

The province was not visited by Alexander, who contented himself with the tributary acknowledgment of his sovereignty made by Ariarathes before the conqueror’s departure from Asia Minor; and the continuity of the native dynasty was only interrupted for a short time after Alexander’s death, when the kingdom fell, in the general partition of the empire, to Eumenes. His claims were made good in 322 by the regent Perdiccas, who crucified Ariarathes; but in the dissensions following Eumenes’s death, the son of Ariarathes recovered his inheritance and left it to a line of successors, who mostly bore the name of the founder of the dynasty, Under the fourth of the name Cappadocia came into relations with Rome, first as a foe espousing the cause of Antiochus the Great, then as an ally against Perseus of Macedon. The kings henceforward threw in their lot with the Republic as against the Seleucids, to whom they had been from time to time tributary. Ariarathes V. marched with the Roman proconsul Crassus against Aristonicus, a claimant to the throne of Pergammum, and their forces were annihilated (130 b.c.). The imbroglio which followed his death ultimately led to interference by the rising power of Pontus and the intrigues and wars which ended in the failure of the dynasty. The Cappadocians, supported by Rome against Mithradates, elected a native lord, Ariobarzanes, to succeed (93 b.c.); but it was not till Rome had disposed at once of the Pontic and Armenian kings that his rule was established (63 b.c.). In the civil wars Cappadocia was now for Pompey, now for Caesar, now for Antony, now against him. The Ariobarzanes dynasty came to an end and a certain Archelaus reigned in its stead, by favour first of Antony, then of Octavian, and maintained tributary independence till a.d. 17, when the emperor Tiberius, on Archelaus’s death in disgrace, reduced Cappadocia at last to a province. Vespasian in a.d. 70 288 joined Armenia Minor to it and made the combined province a frontier bulwark. It remained, under various provincial redistributions, part of the Eastern Empire till late in the 11th century, though often ravaged both by Persians and Arabs. But before it passed into Seljuk hands (1074), and from them ultimately to the Osmanlis, it had already become largely Armenian in religion and speech; and thus we find the southern part referred to as “Hermeniorum terra” by crusading chroniclers. At this day the north-east and east parts of the province are largely inhabited by Armenians. The native kings had done much to Hellenize Cappadocia, which had previously received a strong Iranian colour; but it was left to Christianity to complete their work. Though pre-Hellenic usages long survived in the local cults and habits, a part of the people has remained more or less Hellenic to this day, in spite of its envelopment by Moslem conquerors and converts. The tradition of its early church, illuminated by the names of the two Gregories and Basil of Caesarea, has been perpetuated by the survival of a native Orthodox element throughout the west and north-west of the province; and in the remoter valleys Greek speech has never wholly died out. Its use has once more become general under Greek propagandist influence, and the Cappadocian “Greeks” are now a flourishing community.

CAPPEL, a French family which produced some distinguished jurists and theologians in the 15th and 16th centuries. In 1491, Guillaume Cappel, as rector of the university of Paris, protested against a tithe which Innocent VIII. claimed from that body. His nephew, Jacques Cappel (d. 1541), the real founder of the family, was himself advocate-general at the parlement of Paris, and in a celebrated address delivered before the court in 1537, against the emperor Charles V., claimed for Francis I. the counties of Artois, Flanders and Charolais. He left nine children, of whom three became Protestants. The eldest, Jacques (1529-1586), sieur du Tilloy, wrote several treatises on jurisprudence. Louis (1534-1586), sieur de Moriambert, the fifth son, was a most ardent Protestant. In 1570 he presented a confession of faith to Charles IX. in the name of his co-religionists. He disputed at Sedan before the duc de Bouillon with the Jesuit, Jean Maldouat (1534-1583), and wrote in defence of Protestantism. The seventh son, Ange (1537-1623), seigneur du Luat, was secretary to Henry IV., and enjoyed the esteem of Sully. Among those who remained Catholic should be mentioned Guillaume, the translator of Machiavelli. The eldest son Jacques also left two sons, famous in the history of Protestantism:—Jacques (1570-1624), pastor of the church founded by himself on his fief of le Tilloy and afterwards at Sedan, where he became professor of Hebrew, distinguished as historian, philologist and exegetical scholar; and Louis (see below).

CAPPEL, LOUIS (1585-1658), French Protestant divine and scholar, a Huguenot whose descent is traced above, was born at St Elier, near Sedan, in 1585. He studied theology at Sedan and Saumur; and Arabic at Oxford, where he spent two years. At the age of twenty-eight he accepted the chair of Hebrew at Saumur, and twenty years afterwards was appointed professor of theology. Amongst his fellow lecturers were Moses Amyraut and Josué de la Place. As a Hebrew scholar he made a special study of the history of the Hebrew text, which led him to the conclusion that the vowel points and accents are not an original part of the Hebrew language, but were inserted by the Massorete Jews of Tiberias, not earlier than the 5th century a.d., and that the primitive Hebrew characters are those now known as the Samaritan, while the square characters are Aramaic and were substituted for the more ancient at the time of the captivity. These conclusions were hotly contested by Johannes Buxtorf, being in conflict with the views of his father, Johannes Buxtorf senior, notwithstanding the fact that Elias Levita had already disputed the antiquity of the vowel points and that neither Jerome nor the Talmud shows any acquaintance with them. His second important work, Critica Sacra, was distasteful from a theological point of view. He had completed it in 1634; but owing to the fierce opposition with which he had to contend, he was only able to print it at Paris in 1650, by aid of a son, who had turned Catholic. The various readings in the Old Testament text and the differences between the ancient versions and the Massoretic text convinced him that the idea of the integrity of the Hebrew text, as commonly held by Protestants, was untenable. This amounted to an attack on the verbal inspiration of Scripture. Bitter, however, as was the opposition to his views, it was not long before his results were accepted by scholars.

CAPPELLO, BIANCA (1548-1587), grand duchess of Tuscany, was the daughter of Bartolommeo Cappello, a member of one of the richest and noblest Venetian families, and was famed for her great beauty. At the age of fifteen she fell in love with Pietro Bonaventuri, a young Florentine clerk in the firm of Salviati, and on the 28th of November 1563 escaped with him to Florence, where they were married and she had a daughter named Pellegrina. The Venetian government made every effort to have Bianca arrested and brought back, but the grand duke Cosimo de’ Medici intervened in her favour and she was left unmolested. However she did not get on well with her husband’s family, who were very poor and made her do menial work, until at last her beauty attracted Francesco, the grand duke’s son, a vicious and unprincipled rake. Although already married to the virtuous and charming Archduchess Giovanna of Austria, he seduced the fair Venetian and loaded her with jewels, money and other presents. Bianca’s accommodating husband was given court employment, and consoled himself with other ladies; in 1572 he was murdered in the streets of Florence in consequence of some amorous intrigue, though possibly Bianca and Francesco were privy to the deed. On the death of Cosimo in 1574 Francesco succeeded to the grand duchy; he now installed Bianca in a fine palace close to his own and outraged his wife by flaunting his mistress before her. As Giovanna had borne Francesco no sons, Bianca was very anxious to present him with an heir, for otherwise her position would remain very insecure. But although she resorted to all sorts of expedients, even to that of trying to pass off a changeling as the grand duke’s child, she was not successful. In 1578 Giovanna died; a few days later Francesco secretly married Bianca, and on the 10th of June, 1579, the marriage was publicly announced. The Venetian government now put aside its resentment and was officially represented at the magnificent wedding festivities, for it saw in Bianca Cappello an instrument for cementing good relations with Tuscany. But the long expected heir failed to come, and Bianca realized that if her husband were to die before her she was lost, for his family, especially his brother Cardinal 289 Ferdinand, hated her bitterly, as an adventuress and interloper. In October 1587 both the grand duke and his wife died of colic within a couple of days of each other. At the time poison was suspected, but documentary evidence has proved the suspicion to be unfounded.

CAPPERONNIER, CLAUDE (1671-1744), French classical scholar, the son of a tanner, was born at Montdidier on the 1st of May 1671. He studied at Amiens and Paris, and took orders in the Church of Rome, but devoted himself almost entirely to classical studies. He declined a professorship in the university of Bâle, and was afterwards appointed (1722) to the Greek chair in the Collège de France. He published an edition of Quintilian (1725) and left behind him at his death an edition of the ancient Latin Rhetoricians, which was published in 1756. He furnished much material for Robert Estienne’s Thesaurus Linguae Latinae. His nephew, Jean Capperonnier (1716-1775), his successor in the chair of Greek at the Collège de France, was also a distinguished scholar, and published valuable editions of classical authors—Caesar, Anacreon, Plautus, Sophocles.

CAPPONI, GINO, Marquis (1792-1876), Italian statesman and historian, was born on the 13th of September 1792. The Capponi family is one of the most illustrious Florentine houses, and is mentioned as early as 1250; it acquired great wealth as a mercantile and banking firm, and many of its members distinguished themselves in the service of the republic and the Medicis (see Capponi, Piero), and later in that of the house of Lorraine. Gino was the son of the Marquis Pier Roberto Capponi, a nobleman greatly attached to the reigning grand duke of Tuscany, Ferdinand III. When that prince was deposed by the French in 1799 the Capponi family followed him into exile at Vienna, where they remained until he exchanged his rights to the grand duchy for a German principality (1803). The Capponi then returned to Florence, and in 1811 Gino married the marchesina Giulia Riccardi. Although the family were very anti-French Gino was chosen with other notables to pay homage to Napoleon in Paris in 1813. On the fall of Napoleon Ferdinand returned to Tuscany (September 1814), but the restoration proved less reactionary there than in any other part of Italy. Young Capponi was well received at court, but not being satisfied with the life of a mere man of fashion, he devoted himself to serious study and foreign travel. After sundry journeys in Italy he again visited Paris in 1818, and then went to England. He became deeply interested in English institutions, and carefully studied the constitution, the electoral system, university life, industrial organization, &c. At Edinburgh he met Francis Jeffrey, the editor of the Edinburgh Review, and conceived a desire to found a similar review in Italy. Besides knowing Jeffrey he made the acquaintance of many prominent statesmen and men of letters, including Lord John Russell, the duke of Bedford, Dugald Stewart, Ugo Foscolo, &c. This visit had a great effect in forming his character, and while it made him an ardent Anglophil, he realized more and more the distressing conditions of his own country. He returned to Italy in 1820, and on reaching Florence he set to work to found a review on the lines of the Edinburgh, which should attract the best literary talent. This he achieved with the help of the Swiss G.P. Vieusseux, and the result was the Antologia. He contributed largely to its columns, as well as to those of the Archivio Storico, another of Vieusseux’s ventures. Capponi began to take a more active interest in politics, and entered into communication with the Liberals of all parts of Italy. He had discussed the possibility of liberating Italy with Prince Charles Albert of Savoy-Carignano, to whom he had introduced the Milanese revolutionist Count Confalonieri (q.v.). But the collapse of the rising of 1821 and the imprisonment of Confalonieri made Capponi despair of achieving anything by revolution, and he devoted himself to the economic development of Tuscany and to study. At his beautiful villa of Varramista he collected materials for a history of the Church; his work was interrupted by family troubles and by increasing blindness, but although by 1844 he had completely lost his sight he continued to work by means of amanuenses. In 1847 he again plunged into politics and discussed plans for an Italian alliance against Austria. When the grand duke Leopold II. decided in 1848 to grant his people a constitution, Capponi was made a member of the commission to draw it up, and he eventually became prime minister. During his short tenure of office he conducted foreign affairs with great skill, and made every effort to save the Italian situation after the defeat of Charles Albert on the Mincio. In October 1848 he resigned; soon afterwards the grand duke fled, anarchy followed, and then in 1849 he returned, but with an escort of Austrian soldiery. The blind statesman thanked God that he could not see the hated white uniforms in Florence. He returned to his studies and commenced his great Storia della Repubblica di Firenze; but he followed political affairs with great interest, and helped to convince Lord John Russell, who stayed with him in 1859, of the hopelessness of the grand duke’s position. On Leopold’s second flight (27th of April 1859) a Tuscan assembly was summoned, and Capponi elected member of it. He voted for the grand duke’s deposition and for the union of Tuscany with Piedmont. King Victor Emmanuel made him senator in 1860. His last years were devoted almost exclusively to his Florentine history, which was published in 1875 and achieved an immediate success. This was Capponi’s swan song, for on the 3rd of February 1876 he died at the age of eighty-four.

Capponi was one of the best specimens of the Tuscan landlord class. “He represents,” wrote his biographer Tabarrini, “one of the most striking personalities of a generation, now wholly passed away, which did not resign itself to the beatitudes of 1815, but wished to raise Italy from the humble state to which the European peace of that year had condemned her; and he succeeded by first raising the character of the Italians in the opinion of foreigners, so as to deserve their esteem and respect.” He knew nearly all the most interesting people in Italy, besides many distinguished foreigners: Giuseppe Giusti, the poet, A. Manzoni, the novelist, Niccolò Tommaseo, Richard Cobden, A. von Reumont, the historian, were among those whom he entertained at his palace or his villas, and many were the struggling students and revolutionists to whom he gave assistance. As a historian his reputation rests on his Storia della Repubblica di Firenze (Florence, 1875); it was the first comprehensive Italian book on the subject based on documents and written in a modern critical spirit, and if the chapters on the early history of the city are now obsolete in view of recent discoveries, yet, as a whole, it remains a standard work. Besides his history a large number of essays and pamphlets have been published in his Scritti Inediti.

CAPPONI, PIERO (1447-1496), Florentine statesman and warrior. He was at first intended for a business career, but Lorenzo de’ Medici, appreciating his ability, sent him as ambassador to various courts, where he acquitted himself with distinction. On the death of Lorenzo (1492), who was succeeded by his son, the weak and incapable Piero, Capponi became one of the leaders of the anti-Medicean faction which two years later expelled him from Florence. Capponi was then made chief of the republic and conducted public affairs with great skill, notably in the difficult negotiations with Charles VIII. of France, who had invaded Italy in 1494 and in whose camp the exiled Medici had taken refuge. In November Charles, on his way to Naples, entered Florence with his army, and immediately began to behave as though he were the conqueror of the city, because he had entered it lance in rest. The signory was anxious to be on good terms with him, but when he spoke in favour of the Medici their temper changed at once, and the citizens were ordered to arm and be prepared for all emergencies. Tumults broke out between French soldiers and Florentine citizens, barricades were erected and stones began to fly from the windows. This alarmed Charles, who lowered his tone and said nothing more 290 about conquered cities or the Medici. The Florentines were willing to pay him a large sum of money, but in settling the amount further disagreements arose. Charles, who was full of the Medici’s promises, made exorbitant demands, and finally presented an ultimatum to the signory, who rejected it. “Then we shall sound our trumpets,” said the king, to which Capponi replied “And we shall toll our bells,” and tore up the ultimatum in the king’s face. Charles, who did not relish the idea of house-to-house fighting, was forced to moderate his claims, and concluded a more equitable treaty with the republic. On the 28th of November he departed, and Capponi was appointed to reform the government of Florence. But being more at home in the camp than in the council chamber, he was glad of the opportunity of leading the armies of the republic against the Pisan rebels. He proved a most capable general, but while besieging the castle of Soiana, he was killed on the 25th of September 1496. His death was greatly regretted, for the Florentines recognized in him their ablest statesman and warrior.

CAPRAIA (anc. Capraria, from Lat. capra, wild-goat), an island of Italy, off the N.W. coast (the highest point 1466 ft. above sea-level), belonging to the province of Genoa, 42 m. S.S.E. of Leghorn by sea. Pop. (1901) 547. It is of volcanic origin, and is partly occupied by a penal agricultural colony. It produces wine, and is a centre of the anchovy fishery. It became Genoese in 1527 and was strongly fortified. In 1796 it was occupied for a short time by Nelson. About 20 m. to the north is the island of Gorgona (highest point 836 ft.), also famous for its anchovies.

CAPRERA, an island off the N.E. coast of Sardinia, about 1 m. in length. It is connected by a bridge with La Maddalena. Its chief interest lies in its connexion with Garibaldi, who first established himself there in 1854, and died there on the 2nd of June 1882. His tomb is visited on this anniversary by Italians from all parts. Roman remains, including a bust of Maximian, have been found upon the island.

CAPRI (anc. Capreae), an island on the S. side of the Bay of Naples, of which it commands a fine view; it forms part of the province of Naples, and is distant about 20 m. S. of the town of Naples. Pop. (1901) of the commune of Capri, 3890, of Anacapri, 2316. It divides the exits from the bay into two, the Bocca Grande, about 16 m. wide, between Capri and Ischia, and the Bocca Piccola, 3 m. wide between Capri and the extreme south-west point of the peninsula of Sorrento. It is 4 m. in length and the greatest width is 1½ m., the total area being 5½ sq. m. The highest point is the Monte Solaro (1920 ft.) on the west, while at the east end the cliffs rise to a height of 900 ft. sheer from the sea. The only safe landing-place is on the north side. There are two small towns, Capri (450 ft.) and Anacapri (980 ft.), which until the construction of a carriage road in 1874 were connected only by a flight of 784 steps (the substructures of which at least are ancient). The island lacks water, and is dusty during drought, but is fertile, producing fruit, wine and olive oil; the indigenous flora comprises 800 species. The fishing industry also is important. But the prosperity of the island depends mainly upon foreign visitors (some 30,000 annually), who are attracted by the remarkable beauty of the scenery (that of the coast being especially fine), the views of the sea and of the Bay of Naples, and the purity of the air. The famous Blue Grotto, the most celebrated of the many caves in the rocky shores of the island, was known in Roman times, but lost until 1826, when it was rediscovered. Another beautiful grotto has green instead of blue refractions; the effect in both cases is due to the light entering by a small entrance.

The high land in the west of the island and the somewhat less elevated region in the east are formed of Upper Tithonian and Lower Cretaceous limestones, the latter containing Rudistes. The intervening depression, which seems to be bounded on the west by a fault, is filled to a large extent by sandstones and marls of Eocene age. A superficial layer of recent volcanic tuffs occurs in several parts of the island. The Blue Grotto is in the Tithonian limestones; it shows indications of recent changes of level.

The earliest mythical inhabitants (though some have localized the Sirens here) are the Teleboi from Acarnania under their king Telon. Neolithic remains were found in 1882 in the Grotta delle Felci, a cave on the south coast. In historical times we find the island occupied by Greeks. It subsequently fell into the hands of Neapolis, and remained so until the time of Augustus, who took it in exchange for Aenaria (Ischia) and often resided there. Tiberius, who spent the last ten years of his life at Capri, built no fewer than twelve villas there; to these the great majority of the numerous and considerable ancient remains on the island belong. All these villas can be identified with more or less certainty, the best preserved being those on the east extremity, consisting of a large number of vaulted substructures and the foundations perhaps of a pharos (lighthouse). One was known as Villa Jovis, and the other eleven were probably named after other deities. The existence of numerous ancient cisterns shows that in Roman as in modern times rain-water was largely used for lack of springs. After Tiberius’s death the island seems to have been little visited by the emperors, and we hear of it only as a place of banishment for the wife and sister of Commodus. The island, having been at first the property of Neapolis, and later of the emperors, never had upon it any community with civic rights. Even in imperial times Greek was largely spoken there, for about as many Greek as Latin inscriptions have been found. The medieval town was on the north side at the chief landing-place (Marina Grande), and to it belonged the church of S. Costanzo, an early Christian building. It was abandoned in the 15th century on account of the inroads of pirates, and the inhabitants took refuge higher up at the two towns of Capri and Anacapri.

In 1806 the island was taken by the English fleet under Sir Sidney Smith, and strongly fortified, but in 1808 it was retaken by the French under Lamarque. In 1813 it was restored to Ferdinand I. of the Two Sicilies.

CAPRICCIO, or Caprice (Ital. for a sudden motion or fancy), a musical term for a lively composition of an original and fantastic nature, not following a set musical form, although the first known, written for the harpsichord, partook of the nature of a fugue. The word is also used for pieces of a fanciful type, in the nature of transcriptions and variations.

CAPRICORNUS (“The Goat”), in astronomy, the tenth sign of the zodiac (q.v.), represented by the symbol intended to denote the crooked horns of this animal. The word is derived from Lat. caper, a goat, and cornu, a horn. It is also a constellation of the southern hemisphere, mentioned by Eudoxus (4th century b.c.) and Aratus (3rd century b.c.); Ptolemy and Tycho Brahe catalogued 28 stars, Hevelius gave 29. It was represented by the ancients as a creature having the forepart a goat, and the hindpart a fish, or sometimes simply as a goat. An interesting member of this constellation is α-Capricorni, a pair of stars of 3rd and 4th magnitudes, each of which has a companion of the 9th magnitude.

CAPRIFOLIACEAE, a natural order of plants belonging to the sympetalous or higher division of Dicotyledons, that namely which is characterized by having the petals of the flower united. The plants are mainly shrubs and trees; British representatives are Sambucus (elder), Viburnum (guelder-rose and wayfaring tree), Lonicera (honeysuckle) (see fig.); Adoxa (moschatel), a small herb with a creeping stem and small yellowish-green flowers, is occasionally found on damp hedge-banks; Linnaea, a slender creeping evergreen with a thread-like stem and pink bell-shaped 291 flower, a northern plant, occurs in fir-forests and plantations in the north of England and Scotland. The leaves are opposite, simple as in honeysuckle, or compound as in elder; they have usually no stipules. The flowers are regular as in Viburnum

and Sambucus, more rarely two-lipped as in Lonicera; the sepals and petals are usually five in number and placed above the ovary, the five stamens are attached to the corolla-tube, there are three to five carpels, and the fruit is a berry as in honeysuckle or snowberry (Symphoricarpus), or a stone fruit, with several, usually three, stones, as in Sambucus.

In Sambucus and Viburnum the small white flowers are massed in heads; honey is secreted at the base of the styles and, the tube of the flower being very short, is exposed to the visits of flies and insects with short probosces. The flowers of Lonicera, which have a long tube, open in the evening, when they are sweet-scented and are visited by hawk-moths. The order contains about 250 species, chiefly natives of the north temperate zone and the mountains of the tropics. Several genera afford ornamental plants; such are Lonicera, erect shrubs or twiners with long-tubed white, yellow or red flowers; Symphoricarpus, a North American shrub, with small whitish pendulous flowers and white berries; Diervilla (also known as Weigelia), and Viburnum, including V. Opulus, guelder rose, in the cultivated forms of which the corolla has become enlarged at the expense of the essential organs and the flowers are neuter.

CAPRIVI DE CAPRERA DE MONTECUCCOLI, GEORG LEO VON, Count (1831-1899), German soldier and statesman, was born on the 24th of February 1831 at Charlottenburg. The family springs from Carniola, and the name was originally written Kopriva; in the 18th century one branch settled in Wernigerode, and several members entered the Prussian service; the father of the chancellor held a high judicial post, and was made a life member of the Prussian House of Lords. Caprivi was educated in Berlin, and entered the army in 1849; he took part in the campaign of 1866, being attached to the staff of the ist army. In 1870 he served as chief of the staff to the 10th army corps, which formed part of the 2nd army, and took part in the battles before Metz as well as in those round Orleans, in which he highly distinguished himself. One of the most delicate strategical problems of the whole war was the question of whether to change the direction of the 10th corps on the morning of the 16th of August before Vionville, and in this, as well as in the actual manoeuvres of the corps on that day, Caprivi, as representative of, and counsellor to, his chief, General v. Voigts-Rhetz, took a leading part. At the battle of Beaune-la-Rolande, the turning-point of the Orleans campaign, the 10th corps bore the brunt of the fighting. After the peace he held several important military offices, and in 1883 was made chief of the admiralty, in which post he had to command the fleet and to organize and represent the department in the Reichstag. He resigned in 1888, when the command was separated from the representation in parliament, and was appointed commander of the 10th army corps. Bismarck had already referred to him as a possible successor to himself, for Caprivi had shown great administrative ability, and was unconnected with any political party; and in March 1890 he was appointed chancellor, Prussian minister president and foreign minister. He was quite unknown to the public, and the choice caused some surprise, but it was fully justified. The chief events of his administration, which lasted for four years, are narrated elsewhere, in the article on Germany. He showed great ability in quickly mastering the business, with which he was hitherto quite unacquainted, as he himself acknowledged; his speeches in the Reichstag were admirably clear, dignified and to the point. His first achievement was the conclusion in July 1890 of a general agreement with Great Britain regarding the spheres of influence of the two countries in Africa. Bismarck had supported the colonial parties in Germany in pretensions to which it was impossible for Great Britain to give her consent, and the relations between the two powers were in consequence somewhat strained. Caprivi adopted a conciliatory attitude, and succeeded in negotiating terms with Lord Salisbury which gave to Germany all she could reasonably expect. But the abandonment of an aggressive policy in East Africa and in Nigeria, and in the withdrawal of German claims to Zanzibar (in exchange for Heligoland) aroused the hostility of the colonial parties, who bitterly attacked the new chancellor. Caprivi had, however, by making the frontiers of the Congo Free State and German East Africa meet, “cut” the Cape to Cairo connexion of the British, an achievement which caused much dismay in British colonial circles, regular treaties having been obtained from native chiefs over large areas which the chancellor secured for Germany. In Nigeria also Caprivi by the 1890 agreement, and by another concluded in 1893, made an excellent bargain for his country, while in South-West Africa he obtained a long but narrow extension eastward to the Zambezi of the German protectorate (this strip of territory being known as “Caprivi’s Finger”). In his African policy the chancellor proved far-sighted, and gained for the new protectorates a period for internal development and consolidation. The Anglo-German agreement of 1890 was followed by commercial treaties with Austria, Rumania, &c.; by concluding them he earned the express commendation of the emperor and the title of count, but he was from this time relentlessly attacked by the Agrarians, who made it a ground for their distrust that he was not himself a landed proprietor; and from this time he had to depend much on the support of the Liberals and other parties who had been formerly in opposition. The reorganization of the army caused a parliamentary crisis, but he carried it through successfully, only, however, to earn the enmity of the more old-fashioned soldiers, who would not forgive him for shortening the period of service. His position was seriously compromised by the failure in 1892 to carry an education bill which he had defended by saying that the question at issue was Christianity or Atheism, and he resigned the presidency of the Prussian ministry, which was then given to Count Eulenburg. In 1894, a difference arose between Eulenburg and Caprivi concerning the bill for an amendment of the criminal code (the Umsturz Vorlage), and in October the emperor dismissed both. Caprivi’s fall was probably the work of the Agrarians, but it was also due to the fact that, while he showed very high ability in conducting the business of the country, he made no attempt to secure his personal position by forming a party either in parliament or at court. He interpreted his position rather as a soldier; he did his duty, but did not think of defending himself. He 292 suffered much from the attacks made on him by the followers of Bismarck, and he was closely associated with the social ostracism of that statesman; we do not know, however, in regard either to this or to the other events of his administration, to what extent Caprivi was really the author of the policy he carried out, and to what extent he was obeying the orders of the emperor. With a loyalty which cannot be too highly praised, he always refused, even after his abrupt dismissal, to justify himself, and he could not be persuaded even to write memoirs for later publication. The last years of his life were spent in absolute retirement, for he could not return even to the military duties which he had left with great reluctance at the orders of the emperor. He died unmarried on the 6th of February 1899, at the age of sixty-eight.

CAPRONNIER, JEAN BAPTISTE (1814-1891), Belgian stained-glass painter, was born in Brussels in 1814, and died there in 1891. He had much to do with the modern revival of glass-painting, and first made his reputation by his study of the old methods of workmanship, and his clever restorations of old examples, and copies made for the Brussels archaeological museum. He carried out windows for various churches in Brussels, Bruges, Amsterdam and elsewhere, and his work was commissioned also for France, Italy and England. At the Paris Exhibition of 1855 he won the only medal given for glass-painting.

CAPSICUM, a genus of plants, the fruits of which are used as peppers (see Cayenne Pepper for botany, &c.). As used in medicine, the ripe fruit of the capsicum mimum (or frutescans), containing the active principle capsaicin (capsacutin), first isolated by Thresh in 1876, has remarkable physiological properties. Applied locally to the skin or mucous membrane, it causes redness and later vesication. Internally in small doses it stimulates gastric secretions and causes dilatation of the vessels; but if used internally in excess for a long period it will cause subacute gastritis. In single doses in excess it causes renal irritation and inflammation and strangury. The administration of capsicum is valuable in atony of the stomach due to chronic alcoholism, its hot stimulating effect not only increasing the appetite but to a certain degree satisfying the craving for alcohol. It is also useful in the flatulency of the aged, where it prevents the development of gas, and has a marked effect on anorexia. It has been used in functional torpidity of the kidney. Externally capsicum plaster placed over the affected muscles is useful in rheumatism and lumbago. Capsicum wool, known as calorific wool, made by dissolving the oleoresin of capsicum in ether and pouring it on to absorbent cotton-wool, is useful in rheumatic affections.

CAPSTAN (also spelt in other forms, or as “capstock” and “cable stock,” connected with the O. Fr. capestan or cabestan, from Lat. capistrum, a halter, capere, to take hold of; the conjecture that it came from the Span. cabra, goat, and estanto, standing, is untenable), an appliance used on board ship and on dock walls, for heaving-in or veering cables and hawsers, whether of iron, steel or hemp. It differs from a windlass, which is used for the same purposes, in having the axis on which the rope is wound vertical instead of horizontal. The word seems to have come into English (14th century) from French or Spanish shipmen at the time of the Crusades. The earlier forms were of a comparatively simple character, made of wood with an iron spindle and worked by manual labour with wooden capstan bars. As heavier cables were supplied to ships, difficulty was found, when riding at anchor, in holding, checking and veering cable. A cable-holder (W.H. Harfield’s) was tested in H.M.S. “Newcastle” (wooden frigate) in 1870 and proved effective; its first development in 1876 was the application in the form of a windlass secured to the deck, driven by a messenger chain from the capstan, fitted in H.M.S. “Inflexible” (fig. 1).

The capstans and engine are shown at A, A, A, and the windlass B is driven by messenger chains C, C. The four cables (dotted line D, D) lead to their respective cable-holders, fitted with a brake, and by these means each cable-holder can be connected to the main driving shaft, and any cable hove-in or veered independently of the other; by using steam power instead of manual, the previous slow motion was obviated. In H.M.S. “Collingwood” steam power was used to work the windlass directly by means of worm gearing; the windlass was divided into two parts, so that the one on the port side could be worked independently of that on the starboard, and vice versa. An independent capstan in both ships, arranged to take either of the cables, could be worked by hand or steam. In the “Collingwood’s” windlass the cables remained on their holders, and could be hove-in or veered without being touched.

Napier’s patent windlass for merchant ships (1906) resembles an appliance fitted in the earlier second-class cruisers of the British navy (1890 to 1900). Two cable wheels or cable-holders are mounted loose on a horizontal axle, one on each side of a worm wheel which is tightly keyed on the middle part of the axle. A vertical steam engine with two cylinders, placed one on each side of the framing, drives a second horizontal axle which is connected by a set of bevel gears to an upright worm shaft, which works the worm wheel. This worm wheel can be connected by means of sliding bolts to one or both of the cable wheels, enabling one or both cables to be hove-in or veered as necessary. A brake, of Napier’s self-holding differential type, is fitted to each cable wheel, and is controlled by hand wheels on the aft side of the windlass. For warping purposes, warping drums are fitted (made portable if required). A third central capstan, fitted forward of the windlass, is connected to the upright worm shaft by a horizontal shaft and bevel wheels. It can also be worked by manual labour with capstan bars. Fig. 2 represents the arrangement of the capstans on the forecastle of a battleship, fitted by Napier Brothers. Deep-bodied capstans have been superseded by low drum-headed ones, over which the guns may be fired. The three capstans or cable-holders of cast steel, capable of taking 211⁄16 in. cables, are fitted on vertical spindles, which pass down through the main and armoured decks to the platform one, where the steam engine and gearing are placed. The gearing consists of worm and wheel gears, so arranged that the three capstans can be worked singly or in conjunction, when heaving-in or veering, and the brakes (of the type previously mentioned) are controlled by a portable hand wheel fitted on the aft side of each. The cable-holders can be used for riding at anchor (see Cable). The middle line capstan E is keyed to vertical spindles and can be coupled up to the capstan engine, by clutch and drop bolts in the capstan engine room; it is fitted with a cable-holder, to take either the port or starboard cables, and in addition is provided with portable whelps, enabling it to be used for warping. It can also be worked by manual labour with capstan bars, a drum-head E’, fitted on the spindle on the main deck, enabling additional capstan bars to be used if required.

To avoid carrying steam pipes aft, the after capstan is worked 293 by an electric motor which is kept below the water-line. Napier Brothers’ capstan (fig. 3) is for warping purposes, for working the stern anchor with wire hawser and for coaling. It is placed on the upper deck, and is fitted with a drum-head for capstan bars, with pawls and pawl rim on the deck plate, the pawls A being lifted and placed on their rests B when working with the motor. The upper portion of the capstan, together with its drum-head, is portable, being fixed to the centre boss with keys and gun-metal screws. The centre boss is keyed to the spindle, which passes through the deck and carries at its lower end a coupling for connecting to the worm wheel gear. For working by motor, the additional security of two drop bolts is provided. The gearing consists of a single worm and worm wheel, working in an oil-bath, the worm shaft being coupled direct to the motor spindle. The motor is of the semi-enclosed type, the working and live parts being protected by a perforated metallic covering; it is worked off a 100-volt circuit, at a speed under full load conditions of 300 revolutions per minute. The motor is of a 4-pole type and compound wound, the shunt winding limiting the speed on light load to not more than 1000 revolutions per minute. A frictional break is provided, pulled off by means of a shunt-excited magnet. The controller is of the reversing drum type, with not less than four steps in either direction, and is fitted with a magnetic blow-out. The control is effected by a removable hand wheel on a portable pedestal, fitted on top with a circular dial plate and indicating pointer; the hand wheel reverses the current as well as graduates the speed in either direction. All capstans of the British navy, after being fitted on board ship, are tested for lifting power and speed; with foremost (steam) capstans, the steam being at 150 ℔ pressure, the anchor is usually let go in 16 to 25 fathoms water, and the speed ascertained by observing the time taken to heave-in not less than a length of cable, 75 ft.; the length must be hove-in in three minutes, or at the rate of 25 ft. per minute. With the after capstan (motor) of first-class battleships and cruisers, a weight is used instead of an anchor, the test being to lift 9 tons at the rate of 25 ft. per minute. Capstans on dock walls in British government dockyards are usually driven by hydraulic or air pressure, conveyed through pipes to small engines underneath the capstans.

CAPSULE (from the Lat. capsula, a small box), a term in botany for a dry seed vessel, as in the poppy, iris, foxglove, &c., containing one or more cells. When ripe the capsule opens and scatters the seed (see Botany). The word is used also for a small gelatinous case enclosing a dose of medicine, and for a metal cap or cover on bottles and jars. In anatomy the term is used to denote a cover or envelope partly or wholly surrounding a structure. Every diarthrodial joint possesses a fibrous or ligamentous capsule, lined with synovial membrane, attached to the adjacent ends of the articulating bones. The term is particularly applied to the sac which encloses the crystalline lens of the eye; to Glisson’s capsule, a thin areolar coat of fibrous tissue lying inside the tunica serosa of the liver; to the glomerular capsules in the kidney substance; to the suprarenal capsules, two small flattened organs in the epigastric region; and to the internal and external capsules of the brain (see Brain, fig. 14 and explanation).

CAPTAIN (derived from Lat. caput, head, through the Low Lat. capitanus), a chief or leader, in various connexions, but particularly a grade officer in the army or navy.

At sea the name of captain is given to all who command ships whether they belong to the military navy of their country or not, or whether they hold the substantive rank or not. Thus a lieutenant when in command of a vessel is addressed as captain. In France a naval lieutenant is addressed as mon capitaine because he has that comparative rank in the army. The master of a merchant ship is known as her captain. But the name is also used in the strict sense of foreman, or head man, to describe many of the minor or “petty” officers of a British or American man-of-war—the captain of a top, of the forecastle, or of a gun. The title “post captain” in the British navy means simply full captain, and is the equivalent of the French capitaine de vaisseau. It had its origin in the fact that captains appointed to a ship of twenty guns and upwards were included in, or “posted” on, the permanent list of captains from among whom the admirals were chosen. The captain of the fleet is an officer who acts as chief of the staff to an admiral commanding a large force. The position is equivalent to flag rank, but is held by a captain. Staff captain is the highest grade of the officers entrusted with the nayigation of a ship or fleet.

The military rank of captain (Fr. capitaine, Ger. Hauptmann, or in the cavalry, Rittmeister), which was formerly the title of an officer of high rank corresponding to the modern general officer or colonel, has with the gradual subdivision and articulation of armies, come to be applied to the commanders of companies or squadrons, and in general to officers of the grade equivalent to this command (see Officers).

The title of “captain-general” was formerly used in the general sense of a military commander-in-chief, and is still similarly used in Spain. In the Spanish army there are eight captains-general, each of whom has command of a “region” corresponding to an army corps district. The same title was formerly given to the Spanish governors of the colonial provinces in the New World. The official title of the governor of Jamaica is “captain-general and governor-in-chief.”

CAPTAL (Lat. capitalis, “first,” “chief”), a medieval feudal title in Gascony. According to Du Cange the designation captal (capital, captau, capitau) was applied loosely to the more illustrious nobles of Aquitaine, counts, viscounts, &c., probably as capitales domini, “principal lords,” though he quotes more fanciful explanations. As an actual title the word was used only by the lords of Trene, Puychagut, Epernon and Buch. It is best known in connexion with the famous soldier, Jean de Grailly, captal of Bush (d. 1376), the “captal de Buch” par excellence, immortalized by Froissart as the confidant of the Black Prince and the champion of the English cause against France. His active part in the war began in 1364, when he ravaged the country between Paris and Rouen, but was beaten by Bertrand du Guesclin at Cocherel and taken prisoner. Released next year, he received the seigniory of Nemours and took the oath of fealty to the French king, Charles V., but soon resigned his new fief and returned to his allegiance to the English king. In 1367 he took part in the battle of Navarette, in which Du Guesclin was taken prisoner, the captal being entrusted with his safe-keeping. In 1371 Jean de Grailly was appointed constable of Aquitaine, but was taken prisoner next year and interned in the Temple at Paris where, resisting all the tempting offers of the French king, he remained till his death five years later.

CAPTION (Lat. captio, a taking or catching), a term still used in law, especially Scots, for arrest or apprehension. From the obsolete sense of a catching at any possible plea or objection comes the adjective “captious,” i.e. sophistical or fault-finding. The term also has an old legal use, to signify the part of an indictment, &c., which shows where, when and by what authority it is taken, found or executed; so its opening or heading. From this is derived the modern sense of the heading of an article in a book or newspaper.

CAPTIVE (from Lat. capere, to take), one who is captured in warfare. As a term of International Law, it has been displaced by that of “prisoner of war.” The position and treatment of captives or prisoners of war is now dealt with fully in chapter ii. of the regulations annexed to the Hague Convention respecting the Laws and Customs of War on Land, of the 18th of October 1907.

294

CAPTURE (from Lat. capere, to take; Fr. prise maritime; Ger. Wegnahme), in international law, the taking possession by a belligerent vessel of an enemy or neutral merchant or non-fighting ship. If an enemy ship is captured she becomes forthwith lawful prize (q.v.); when a neutral ship, the belligerent commander, in case her papers are not conclusive, has a right to search her. If he finds contraband on board or the papers or cargo or circumstances excite any serious suspicion in his mind, which the master of the ship has been unable to dispel, he places an officer and a few of his crew on board and sends her to the nearest port where there is a prize court for trial. The word is also used for the vessel thus captured (see Blockade, Contraband).

CAPUA (anc. Casilinum), a town and archiepiscopal see of Campania, Italy, in the province of Caserta, 7 m. W. by rail from the town of Caserta. Pop. (1901) 14,285. It was erected in 856 by Bishop Landulf on the site of Casilinum (q.v.) after the destruction of the ancient Capua by the Saracens in 840, but it only occupies the site of the original pre-Roman town on the left (south) bank of the river.

The cathedral of S. Stefano, erected in 856, has a handsome atrium and a lofty Lombard campanile, and a (modernized) interior with three aisles; both it and the atrium have ancient granite columns. The Romanesque crypt, with ancient columns, has also been restored. It has a fine paschal candlestick, and the fragments of a pulpit with marble mosaic of the 13th century. There are also preserved in the cathedral a fine Exultet roll and an evangelarium of the end of the 12th century, bound in bronze decorated with gold filigree and enamels. The mosaics of the beginning of the 12th century in the apses of the cathedral and of S. Benedetto, were destroyed about 1720 and 1620 respectively. The small church of S. Marcello was also built in 856. In 1232-1240 Frederick II. erected a castle to guard the Roman bridge over the Volturno, composed of a triumphal arch with two towers. This was demolished in 1557. The statues with which it was decorated were contemporary imitations of classical sculptures. Some of them are still preserved in the Museo Campano (E. Bertaux, L’Art dans l’Italie méridionale, Paris, 1904, i. 707). The Museo Campano also contains a considerable collection of antiquities from the ancient Capua.

Capua changed hands frequently during the middle ages. One of the most memorable facts in its history is the terrible attack made on it in 1501 by Caesar Borgia, who had entered the town by treachery, in which 5000 lives were sacrificed. It remained a part of the kingdom of Naples until the 2nd of November 1860, when, a month after the battle of the Volturno, it surrendered to the Italian troops.

CAPUA (mod. S. Maria di Capua Vetere), the chief ancient city of Campania, and one of the most important towns of ancient Italy, situated 16 m. N. of Neapolis, on the N.E. edge of the Campanian plain. Its site in a position not naturally defensible, together with the regularity of its plan, indicates that it is not a very ancient town, though it very likely occupies the site of an early Oscan settlement. Its foundation is attributed by Cato to the Etruscans, and the date given as about 260 years before it was “taken” by Rome (Vell. i. 7). If this be referred, not to its capture in the second Punic War (211 b.c.) but to its submission to Rome in 338 b.c., we get about 600 b.c. as the date of its foundation, a period at which the Etruscan power was at its highest, and which may perhaps, therefore, be accepted.1 The origin of the name is probably Campus, a plain,2 as the adjective Campanus shows, Capuanus being a later form stigmatized as incorrect by Varro (De L.L. x. 16). The derivation from κάπυς (a vulture, Latinized into Volturnum by some authorities who tell us that this was the original name), and that from caput (as though the name had been given it as the “head” of the twelve Etruscan cities of Campania), must be rejected. The Etruscan supremacy in Campania came to an end with the Samnite invasion in the latter half of the 5th century b.c. (see Campania); these conquerors, however, entered into alliance with Rome for protection against the Samnite mountain tribes, and with Capua came the dependent communities Casilinum, Calatia, Atella, so that the greater part of Campania now fell under Roman supremacy. The citizens received the civitas sine suffragio. In the second Samnite War they proved untrustworthy, so that the Ager Falernus on the right bank of the Volturnus was taken from them and distributed among citizens of Rome, the tribus Falerna being thus formed; and in 318 the powers of the native officials (meddices) were limited by the appointment of officials with the title praefecti Capuam Cumas (taking their name from the most important towns of Campania); these were at first mere deputies of the praetor urbanus, but after 123 b.c. were elected Roman magistrates, four in number; they governed the whole of Campania until the time of Augustus, when they were abolished. In 312 b.c. Capua was connected with Rome by the construction of the Via Appia, the most important of the military highways of Italy. The gate by which it left the Servian walls of Rome bore the name Porta Capena—perhaps the only case in which a gate in this enceinte bears the name of the place to which it led. At what time the Via Latina was prolonged to Casilinum is doubtful (it is quite possible that it was done when Capua fell under Roman supremacy, i.e. before the construction of the Via Appia); it afforded a route only 6 m. longer, and the difficulties in connexion with its construction were much less; it also avoided the troublesome journey through the Pomptine Marshes (see T. Ashby in Papers of the British School at Rome, i. 217, London, 1902). The importance of Capua increased steadily during the 3rd century, and at the beginning of the second Punic War it was considered to be only slightly behind Rome and Carthage themselves, and was able to furnish 30,000 infantry and 4000 cavalry. Until after the defeat of Cannae it remained faithful to Rome, but, after a vain demand that one of the consuls should always be selected from it, it transferred its allegiance to Hannibal, who made it his winter-quarters, with bad results to the morale of his troops (see Punic Wars). After a long siege it was taken by the Romans in 211 b.c. and severely punished; its magistrates and communal organization were abolished, the inhabitants losing their civic rights, and its territory became Roman state domain. Parts of it were sold in 205 and 199 b.c., another part was divided among the citizens of the new colonies of Volturnum and Liternum established near the coast in 194 b.c., but the greater portion of it was reserved to be let by the state. Considerable difficulties occurred in preventing illegal encroachments by private persons, and it became necessary to buy a number of them out in 162 b.c. It was, after that period, let, not to large but to small proprietors. Frequent attempts were made by the democratic leaders to divide the land among new settlers. Brutus in 83 b.c. actually succeeded in establishing a colony, but it was soon dissolved; and Cicero’s speeches De Lege Agraria were directed against a similar attempt by Servilius Rullus in 63 b.c. In the meantime the necessary organization of the inhabitants of this thickly-populated district was in a measure supplied by grouping them round important shrines, especially that of Diana Tifatina, in connexion with which a pagus Dianae existed, as we learn from many inscriptions; a pagus Herculaneus is also known. The town of Capua belonged to none of these organizations, and was entirely dependent on the praefecti. It enjoyed great prosperity, however, owing to its spelt, which was worked into groats, wine, roses, spices, unguents, &c., and also owing to its manufactures, especially of bronze objects, of which both the elder Cato and the elder Pliny speak in the highest terms (De agr. 135; Hist. Nat. xxiv. 95). Its luxury remained proverbial; and Campania is especially spoken of as the home of gladiatorial combats. From the gladiatorial schools of Campania came Spartacus and his followers in 73 b.c. Julius Caesar as consul in 59 b.c. succeeded in carrying out the establishment of a colony in connexion with his agrarian law, and 20,000 Roman citizens were settled in this territory. The number of colonists was increased by Mark 295 Antony, Augustus (who constructed an aqueduct from the Mons Tifata, and gave the town of Capua estates in the district of Cnossus in Crete to the value of 12 million sesterces—£120,000), and Nero. In the war of a.d. 69 it took the side of Vitellius. Under the later empire it is not often mentioned; but in the 4th century it was the seat of the consularis Campaniae and its chief town, though Ausonius puts it behind Mediolanum (Milan) and Aquileia in his ordo nobilium urbium. Under Constantine we hear of the foundation of a Christian church in Capua. In a.d. 456 it was taken and destroyed by Genseric, but must have been soon rebuilt: it was, however, finally destroyed by the Saracens in 840 and the church of S. Maria Maggiore, founded about 497, alone remained. It contains 52 ancient marble columns, but was modernized in 1766. The site was only occupied in the late middle ages by a village which has, however, outgrown the medieval Capua in modern days.

Remains.—No pre-Roman remains have been found within the town of Capua itself, but important cemeteries have been discovered on all sides of it, the earliest of which go back to the 7th or 6th century b.c. The tombs are of various forms, partly chambers with frescoes on the walls, partly cubical blocks of peperino, hollowed out, with grooved lids. The objects found within them consist mainly of vases of bronze (many of them without feet, and with incised designs of Etruscan style) and of clay, some of Greek, some of local manufacture, and of paintings. On the east of the town, in the Patturelli property, a temple has been discovered with Oscan votive inscriptions, some of them inscribed upon terra-cotta tablets, others on cippi, while of a group of 150 tufa statuettes (representing a matron holding one or more children in her lap) three bore Latin inscriptions of the early imperial period. The site of the town being in a perfectly flat plain, without natural defences, it was possible to lay it out regularly. Its length from east to west is accurately determined by the fact that the Via Appia, which runs from north-west to south-east from Casilinum to Calatia, turns due east very soon after passing the so-called Arco Campano (a triumphal arch of good brickwork, once faced with marble, with three openings, erected in honour of some emperor unknown), and continues to run in this direction for 5413½ English feet (= 6000 ancient Oscan feet). The west gate was the Porta Romana; remains of the east gate (the name of which we do not know) have been found. This fact shows that the main street of the town was perfectly orientated, and that before the Via Appia was constructed, i.e. in all probability in pre-Roman times. The width of the town from north to south cannot be so accurately determined as the line of the north and south walls is not known, though it can be approximately fixed by the absence of tombs (Beloch fixes it at 4000 Oscan feet = 3609 English feet), nor is it absolutely certain (though it is in the highest degree probable, for Cicero praises its regular arrangement and fine streets) that the plan of the town was rectangular. Within the town are remains of thermae on the north of the Via Appia and of a theatre opposite, on the south. The former consisted of a large crypto-porticus round three sides of a court, the south side being open to the road; it now lies under the prisons. Beloch (see below) attributes this to the Oscan period; but the construction as shown in Labruzzi’s drawing (v. 17)3 is partly of brick-work and opus reticulatum, which may, of course, belong to a restoration. The stage of the theatre had its back to the road; Labruzzi (v. 18) gives an interesting view of the cavea. It appears from inscriptions that it was erected after the time of Augustus. Other inscriptions, however, prove the existence of a theatre as early as 94 b.c., so that the existence of another elsewhere must be assumed. We know that the Roman colony was divided into regions and possessed a capitolium, with a temple of Jupiter, within the town, and that the market-place, for unguents especially, was called Seplasia; we also hear of an aedes alba, probably the original senate house, which stood in an open space known as albana. But the sites of all these are quite uncertain. Outside the town on the north is the amphitheatre, built in the time of Augustus, restored by Hadrian and dedicated by Antoninus Pius, as the inscription over the main entrance recorded. The exterior was formed by 80 Doric arcades of four storeys each, but only two arches now remain. The keystones were adorned with heads of divinities. The interior is better preserved; beneath the arena are subterranean passages like those in the amphitheatre at Puteoli. It is one of the largest in existence; the longer diameter is 185 yds., the shorter 152, and the arena measures 83 by 49 yds., the corresponding dimensions in the colosseum at Rome being 205, 170, 93 and 58 yds. To the east are considerable remains of baths—a large octagonal building, an apse against which the church of S. Maria delle Grazie is built, and several heaps of debris. On the Via Appia, to the south-east of the east gate of the town, are two large and well-preserved tombs of the Roman period, known as le Carceri vecchie and la Conocchia. To the east of the amphitheatre an ancient road, the Via Dianae, leads north to the Pagus Dianae, on the west slopes of the Mons Tifata, a community which sprang up round the famous and ancient temple of Diana, and probably received an independent organization after the abolition of that of Capua in 211 b.c. The place often served as a base for attacks on the latter, and Sulla, after his defeat of C. Norbanus, gave the whole of the mountain to the temple. Within the territory of the pagus were several other temples with their magistri. After the restoration of the community of Capua, we find magistri of the temple of Diana still existing, but they were probably officials of Capua itself. The site is occupied by the Benedictine church of S. Angelo in Formis4 which dates from 944, and was reconstructed by the abbot Desiderius (afterwards Pope Victor III.) of Monte Cassino in 1073, with interesting paintings, dating from the end of the 11th century to the middle of the 12th, in which five different styles may be distinguished. They form a complete representation of all the chief episodes of the New Testament (see F.X. Kraus, Jahrbuch d. k. preuss. Kunstsammlungen, xiv.). Deposits of votive objects (favissae), removed from the ancient temple from time to time as new ones came in and occupied all the available space, have been found, and considerable remains of buildings belonging to the Vicus Dianae (among them a triumphal arch and some baths, also a hall with frescoes, representing the goddess herself ready for the chase) still exist.