[1] This is the spelling of the old law-books, as given by Pennant,
the zoologist, who, on something more than mere report, first
included this bird among the British fauna. The only one of the
"Scots Acts," however, in which the present writer has been able to
ascertain that the bird is named is No. 30 of James VI. (1621), which
was passed to protect "powties, partrikes, moore foulles, blakcoks,
gray hennis, termigantis, quailzies, _capercailzies_," &c.
[2] Not to be confounded with the bird so named previously by Prof.
Nilsson, which is a hybrid.
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 ([Greek: Kapernaoum]; probably, "the village of Nahum"), 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-Tabighah_, 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 Hum can be considered as a corruption of _Kefr
Nahum_, 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.
On the site of Capernaum see especially W. Sanday in _Journal of
Theological Studies_, vol. v. p. 42. (R. A. S. M.)
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-Pres, 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-Angouleme followed from Francis I. to the death of Henry III. in
1589 (see ANGOULEME), 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 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 deg.
56' S., 18 deg. 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
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 8-1/2 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 2-1/2 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 L5,128,292, exports
L15,881,952. In 1904, two years after the conclusion of the war the
figures were:--imports L9,070,757; exports L17,471,760. In 1907 during a
period of severe and prolonged trade depression the imports had fallen
to L5,263,930, but the exports owing entirely to the increased output of
gold from the Rand mines had increased to L37,994,658; gold and diamonds
represented over L37,000,000 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
L2,054,204, in 1901 L9,475,260, in 1908 (when the rate levied was 3d. in
the L) L14,129,439. The total rateable value of the suburbs, not
included in the above figures, is over L8,000,000. 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 deg. 13' and 14 deg.
47' N. and 22 deg. 40' and 25 deg. 22' W. Pop. (1905) about 138,620;
area, 1475 sq. m. The archipelago consists of ten islands:--Santo Antao
(commonly miswritten St Antonio), Sao Vicente, Santa Luzia, Sao Nicolao,
Sal, Boa Vista, Maio, Sao 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.
[Illustration: CAPE VERDE Is. map.]
_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 deg. to 90 deg. 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 Antao, Fogo and Sao
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, Sao
Thiago and Fogo; wild boars in Sao 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 Sao Thiago. Turtles come from the
African coast to lay their eggs on the sandy shores. The Ilheu Branco,
or White Islet, between Sao 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 Sao
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 Sao
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 L60,000;
that of the imports (including L200,000 for coal), about L350,000. 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 Sao Vicente, for coal, and do not receive or
discharge any large quantities of cargo.
_Santo Antao_ (pop. 25,000), at the extreme north-west of the
archipelago, has an area of 265 sq. m. Its surface is very rugged and
mountainous, abounding in volcanic craters, of which the chief is the
Topoda Coroa (7300 ft.), also known as the Sugar-loaf. Mineral springs
exist in many places. The island is the most picturesque, the
healthiest, and, on its north-western slope, the best watered and most
fertile of the archipelago. The south-eastern slope, shut out by lofty
mountains from the fertilizing moisture of the trade-winds, has an
entirely different appearance, black rocks, white pumice and red clay
being its most characteristic features. Santo Antao produces large
quantities of excellent coffee, besides sugar and fruit. It has
several small ports, of which the chief are the sheltered and spacious
Tarrafal Bay, on the south-west coast, and the more frequented Ponta
do Sol, on the north-east, 8 m. from the capital, Ribeira Grande, a
town of 4500 inhabitants. Cinchona is cultivated in the neighbourhood.
In 1780 the slaves on Santo Antao were declared free, but this decree
was not carried out. About the same time many white settlers, chiefly
from the Canaries, entered the island, and introduced the cultivation
of wheat.
_Sao Vicente_, or _St Vincent_ (8000), lies near Santo Antao, on the
south-east, and has an area of 75 sq. m. Its highest point is Monte
Verde (2400 ft.). The whole island is as arid and sterile as the
south-eastern half of Santo Antao, and for the same reason. It was
practically uninhabited until 1795; in 1829 its population numbered
about 100. Its harbour, an extinct crater on the north coast, with an
entrance eroded by the sea, affords complete shelter from every wind.
An English speculator founded a coaling station here in 1851, and the
town of Mindello, also known as Porto Grande or St Vincent, grew up
rapidly, and became the commercial centre of the archipelago. Most of
the business is in English hands, and nine-tenths of the inhabitants
understand English. Foodstuffs, wood and water are imported from Santo
Antao, and the water is stored in a large reservoir at Mindello. Sao
Vicente has a station for the submarine cable from Lisbon to
Pernambuco in Brazil.
_Santa Luzia_, about 5 m. south-east, has an area of 18 sq. m., and
forms a single estate, occupied only by the servants or the family of
the proprietor. Its highest point is 885 ft. above sea-level. On the
south-west it has a good harbour, visited by whaling and fishing
boats. Much orchil was formerly gathered, and there is good pasturage
for the numerous herds of cattle. A little to the south are the
uninhabited islets of Branco and Razo.
_Sao Nicolao_, or _Nicolau_ (12,000), a long, narrow, crescent-shaped
island with an area of 126 sq. m., lies farther east, near the middle
of the archipelago. Its climate is not very healthy. Maize,
kidney-beans, manioc, sugar-cane and vines are cultivated; and in
ordinary years grain is exported to the other islands. The interior is
mountainous, and culminates in two peaks which can be seen for many
leagues; one has the shape of a sugar-loaf, and is near the middle of
the island; the other, Monte Gordo, is near the west end, and has a
height of 4280 ft. All the other islands of the group can be seen from
Sao Nicolao in clear weather. Vessels frequently enter Preguica, or
Freshwater Bay, near the south-east extremity of the island, for water
and fresh provisions; and the custom-house is here. The island was one
of the first colonized; in 1774 its inhabitants numbered 13,500, but
famine subsequently caused a great decrease. The first capital, Lapa,
at the end of a promontory on the south, was abandoned during the
period of Spanish ascendancy over Portugal (1580-1640) in favour of
Ribeira Brava (4000), on the north coast, a town which now has a
considerable trade.
_Sal_ (750), in the north-east of the archipelago, has an area of 75
sq. m. It was originally named _Lana_, or _Lhana_ ("plain"), from the
flatness of the greater part of its surface. It derives its modern
name from a natural salt-spring, but most of the salt produced here is
now obtained from artificial salt-pans. Towards the close of the 17th
century it was inhabited only by a few shepherds, and by slaves
employed in the salt-works. In 1705 it was entirely abandoned, owing
to drought and consequent famine; and only in 1808 was the manufacture
of salt resumed. A railway, the first built in Portuguese territory,
was opened in 1835. The hostile Brazilian tariffs of 1889 for a time
nearly destroyed the salt trade. Whales, turtles and fish are
abundant, and dairy-farming is a prosperous industry. There are many
small harbours, which render every part of the island easily
accessible.
_Boa Vista_ (2600), the most easterly island of the archipelago, has
an area of 235 sq. m. It was named Sao Christovao by its discoverers
in the 15th century. Its modern name, meaning "fair view," is
singularly inappropriate, for with the exception of a few coco-nut
trees there is no wood, and in the dry season the island seems nothing
but an arid waste. The little vegetation that then exists is in the
bottom of ravines, where corn, beans and cotton are cultivated. The
springs of good water are few. The coast is indented by numerous
shallow bays, the largest of which is the harbour of the capital,
Porto Sal-Rei, on the western side (pop. about 1000). A chain of
heights, flanked by inferior ranges, traverses the middle of Boa
Vista, culminating in Monte Gallego (1250 ft.), towards the east. In
the north-western angle of the island there is a low tract of loose
sand, which is inundated with water during the rainy season; and here
are some extensive salt-pans, where the sea-water is evaporated by the
heat of the sun. Salt and orchil are exported. A good deal of fish is
taken on the coast and supplies the impoverished islanders with much
of their food.
_Maio_ (1000) has an area of 70 sq. m., and resembles Sal and Boa
Vista in climate and configuration, although it belongs to the
Sotavento group. Its best harbour is that of Nossa Senhora da Luz, on
the south-west coast, and is commonly known as Porto Inglez or English
Road, from the fact that it was occupied until the end of the 18th
century by the British, who based their claim on the marriage-treaty
between Charles II. and Catherine of Braganza (1662). The island is a
barren, treeless waste, surrounded by rocks. Its inhabitants, who live
chiefly by the manufacture of salt, by cattle-farming and by fishing,
are compelled to import most of their provisions from Sao Thiago, with
which, for purposes of local administration, Maio is included.
_Sao Thiago_ (63,000) is the most populous and the largest of the Cape
Verde Islands, having an area of 350 sq. m. It is also one of the most
unhealthy, except among the mountains over 2000 ft. high. The interior
is a mass of volcanic heights, formed of basalt covered with chalk and
clay, and culminating in the central Pico da Antonia (4500 ft.), a
sharply pointed cone. There are numerous ravines, furrowed by
perennial streams, and in these ravines are grown large quantities of
coffee, oranges, sugar-cane and physic-nuts, besides a variety of
tropical fruits and cereals. Spirits are distilled from sugar-cane,
and coarse sugar is manufactured. The first capital of the islands was
Ribeira Grande, to-day called Cidade Velha or the Old City, a
picturesque town with a cathedral and ruined fort. It was built in the
15th century on the south coast, was made an episcopal see in 1532,
and became capital of the archipelago in 1592. In 1712 it was sacked
by a French force, but despite its poverty and unhealthy situation it
continued to be the capital until 1770, when its place was taken by
Praia on the south-east. Praia (often written Praya) has a fine
harbour, a population of 21,000 and a considerable trade. It contains
the palace of the governor-general, a small natural history museum, a
meteorological observatory and an important station for the cables
between South America, Europe and West Africa. It occupies a basalt
plateau, overlooking the bay (Porto da Praia), and has an attractive
appearance, with its numerous coco-nut trees and the peak of Antonia
rising in the background above successive steps of tableland. Its
unhealthiness has been mitigated by the partial drainage of a marsh
lying to the east.
_Fogo_ (17,600) is a mass of volcanic rock, almost circular in shape
and measuring about 190 sq. m. In the centre a still active volcano,
the Pico do Cano, rises to a height of about 10,000 ft. Its crater,
which stands within an older crater, measures 3 m. in circumference
and is visible at sea for nearly 100 m. It emits smoke and ashes at
intervals; and in 1680, 1785, 1799, 1816, 1846, 1852 and 1857 it was
in eruption. After the first and most serious of these outbreaks, the
island, which had previously been called Sao Felippe, was renamed
Fogo, _i.e._ "Fire." The ascent of the mountain was first made in 1819
by two British naval officers, named Vidal and Mudge. The island is
divided, like Santo Antao, into a fertile and a sterile zone. Its
northern half produces fine coffee, beans, maize and sugar-cane; the
southern half is little better than a desert, with oases of cultivated
land near its few springs. Sao Felippe or Nossa Senhora da Luz (3000),
on the west coast, is the capital. The islanders claim to be the
aristocracy of the archipelago, and trace their descent from the
original Portuguese settlers. The majority, however, are negroes or
mulattoes. Drought and famine, followed by severe epidemics, have
been especially frequent here, notably in the years 1887-1889.
_Brava_ (9013), the most southerly of the islands, has an area of 23
sq. m. Though mountainous, and in some parts sterile, it is very
closely cultivated, and, unlike the other islands, is divided into a
multitude of small holdings. The desire to own land is almost
universal, and as the population numbers upwards of 380 per sq. m.,
and the system of tenure gives rise to many disputes, the peasantry
are almost incessantly engaged in litigation. The women, who are
locally celebrated for their beauty, far outnumber the men, who
emigrate at an early age to America. These emigrants usually return
richer and better educated than the peasantry of the neighbouring
islands. To the north of Brava lie a group of reefs among which two
islets (Ilheus Seccos or Ilheus do Rombo) are conspicuous. These are
usually known as the Ilheu de Dentro (Inner Islet) and the Ilheu de
Fora (Outer Islet). The first is used as a shelter for whaling and
fishing vessels, and as pasturage for cattle; the second has supplied
much guano for export.
_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.
The best general account of the islands is given in vols. xxiii. and
xxvii. of the _Boletim_ of the Lisbon Geographical Society (1905 and
1908), and in _Madeira, Cabo Verde, e Guine_, by J.A. Martins (Lisbon,
1891). Official statistics are published in Lisbon at irregular
intervals. See also _Uber die Capverden_ (Leipzig, 1884) and _Die
Vulcane der Capverden_ (Graz, 1882), both by C. Dolter. A useful map,
entitled _Ocean Atlantico Norte, Archipelago do Cabo Verde_, was
issued in 1900 by the _Commissao de Cartographia_, Lisbon.
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 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.
See Potthast, _Bibliotheka Med. Aev_.; and U. Chevalier, _Repertoire
des sources hist. Bio-bibliographie, s.v._
CAP HAITIEN, CAPE HAITIEN 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 deg. 46' N. and 72 deg. 14' W. Its original Indian name
was Guarico, and it has been known, at various times, as Cabo Santo, Cap
Francais 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 (_Theorie 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. Gotting_, 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.
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 (_Memoires 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 (_Mecanique
celeste_, 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 + 1/2H(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_, Gottingen, 1830, or _Werke_, v. 29, Gottingen, 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 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 Simeon Denis Poisson published his _Nouvelle Theorie 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 experimentale et theorique 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 (_Mem. 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 Dupre 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 Dupre 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. Ludtge (_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.