Online Encyclopedia
Search over 40,000 articles from the original, classic Encyclopedia Britannica, 11th Edition.
PEARL
Online EncyclopediaOriginally appearing in Volume
V21,
Page 27
of the 1911 Encyclopedia Britannica.
Encyclopedia Home :: PAS-PER
Spread the word:
del.icio.us it!
del.icio.us it!
|
PEARL . Pearls are calcareous concretions of See also: peculiar lustre, produced by certain molluscs, and valued as See also:objects of See also:personal See also:ornament. The experience of pearl-fishers shows that those shells which are irregular in shape and stunted in growth, or which See also:bear excrescences, or are honeycombed by See also:boring parasites, are those most likely to yield pearls. The substance of a pearl is essentially the same as that which lines the interior of many shells and is known as " See also:mother-of-pearl." See also:Sir D. See also:Brewster first showed that the iridescence of this substance was an See also:optical phenomenon due to the interference of rays of See also:light reflected from microscopic corrugations of the See also:surface —an effect which may be imitated by artificial striations on a suit-able See also:medium. When the inner laminated portion of a nacreous See also:shell is digested in See also:acid the calcareous layers are dissolved away, leaving a very delicate membranous pellicle, which, as shown by Dr See also:Carpenter, may retain the iridescence as See also:long as it is undisturbed, but which loses it when pressed or stretched. It is obvious that if a pearl presents a perfectly spherical See also:form it must have remained loose in the substance of the muscles or other soft tissues of the mollusc. Frequently, however, the pearl becomes cemented to the interior of the shell, the point of See also:attachment thus interfering with its symmetry. In this position it may receive successive nacreous deposits, which ultimately form a pearl of hemispherical shape, so that when cut from the shell it may be See also:flat on one See also:side and See also:convex on the other, forming what jewelers know as a " perle bouton." In the course of growth the pearl may become involved in the See also:general See also:deposit of mother-of-pearl, and be ultimately buried in the substance of the shell. It has thus happened that See also:fine pearls have occasionally been unexpectedly brought to light in cutting up mother-of-pearl in the workshop. When a pearl See also:oyster is attacked by a boring See also:parasite the mollusc protects itself by depositing nacreous See also:matter at the point of invasion, thus forming a hollow See also:body of irregular shape known as a " See also:blister pearl." Hollow warty pearl is sometimes termed in See also:trade " coq de perle." Solid pearls of irregular form are often produced by deposition on rough objects, such as small fragments of See also:wood, and these, and in fact all irregular-shaped pearls, are termed " peries baroques," or " barrok pearls." It appears that the See also:Romans in the See also:period of the Decline restricted the name unio to the globular pearl, and termed the See also:baroque margaritum. It was fashionable in the 16th and 17th centuries to See also:mount curiously shaped baroques in See also:gold and See also:enamel so as to form ornamental objects of See also:grotesque See also:character.A valuable collection of such mounted pearls by Dinglinger is preserved in the See also:
Fishing generally commences in the second See also: week in See also:
The diving continues from sunrise to about See also: noon, when a gun is fired. On the arrival of the See also:fleet at shore the divers carry their oysters to a See also:shed, where they are made up into four heaps. one of which is taken by the diver. The oysters are then sold by See also:auction in lots of r000 each. The pearls, after removal from the dead oysters, are " classed " by passing through a number of small See also:brass colanders, known as " baskets," the holes in the successive vessels being smaller and smaller. Having been sized in this way, they are sorted as to colour, weighed and valued. Since the days of the Macedonians pearl-fishing has been carried on in the Persian Gulf. It is said that the oyster-beds extend along the entire Arabian coast of the gulf, but the most important are on sandbanks off the islands of Bahrein. The See also:chief centre of the trade is the See also:port of Lingah. Most of the products of this fishery are known as " Bombay pearls," from the fact that many of the best are sold there. The shells usually present a dark colour about the edges, like that of " smoked pearl." The yellow-tinted pearls are sent chiefly to Bombay, while the whitest go to See also:Bagdad. Very small pearls, much below a'See also:pea in See also:size, are generally known as " See also:seed-pearls," and these are valued in India and See also:China as constituents of certain electuaries, while occasionally they are calcined for chunam, or See also:lime, used with betel as a masticatory. There is a small pearl-fishery near See also:Karachi on the coast of Bombay.From the time of the See also: Ptolemies pearl-fishing has been prosecuted along the coast of the Red See also:Sea, especially in the neighbourhood of Jiddah and Koseir. This fishery is now insignificant, but the See also:Arabs still obtain from this See also:district a quantity of mother-of-pearl shells, which are shipped from See also:Alexandria, and come into the See also:market as " Egyptians." Very fine pearls are obtained from the Sulu See also:Archipelago, on the See also:north-See also:east of See also:Borneo. The mother-of-pearl shells from the Sulu seas are characterized by a yellow colour on the border and back, which unfits them for many ornamental purposes. Pearl oysters are also abundant in the seas around the Aru Islands to the south-See also:west of New See also:Guinea. From See also:Labuan a See also:good many pearl shells are occasionally sent to See also:Singapore. They are also obtained from the neighbourhood of See also:Timor, and from New See also:Caledonia. The pearl oyster occurs throughout the Pacific, mostly in the clear water of the lagoons within the atolls, though fine shells are also found in deep water outside the See also:coral reefs. The Polynesian divers do not employ sink-stones, and the See also:women are said to be more skilful than the men. They anoint their bodies with oil before diving. Fine pearl-shells are obtained from Navigators' Islands, the Society Islands, the See also:Low Archipelago or Paumota Isles and the See also:Gambier Islands. Many of the Gambier pearls present a bronzy tint. Pearl-fishing is actively prosecuted along the western coast of Central America, especially in the Gulf of See also:California, and to a less extent around the Pearl Islands in the See also:Bay of See also:Panama.The fishing-grounds are in water about 4o ft. deep, and the season of Teh-tsing, where it forms the See also: staple See also:industry of several villages, lasts for four months. An See also:ordinary fishing-party expects to obtain about three tons of shells per See also:day, and it is estimated that one shell in a thousand contains a pearl. The pearls are shipped in barrels from See also:San Francisco and Panama. Some pearls of rare beauty have been obtained from the Bay of Mulege, near Los Coyetes, in the gulf of California; and in 1882 a pearl of 75 carats, the largest on See also:record from this district, was found near La Paz in California. The coast of See also:Guayaquil also yields pearls. See also:Columbus found that pearl-fishing was carried on in his time in the Gulf of See also:Mexico, and pearls are still obtained from the Carib-See also:bean Sea. In the West Indies the best pearls are obtained from St See also:
On the western coast of Australia the pearl-shells are obtained by dredging rather than by diving. Pearl-shells have also been found at Port See also: Darwin and in Oakley See also:Creek, New See also:Zealand. See also:River pearls are produced by the See also:species of Unio and Anodonta, especially by Unio rnargaritiferus. These species belong to the See also:family Unionidae, See also:order Eulamellebranchia. They inhabit the See also:mountain-streams of temperate climates in the See also:northern hemisphere—especially in See also:Scotland, See also:Wales, See also:Ireland, See also:Saxony, Bohemia, See also:Bavaria, See also:Lapland and See also:Canada. The pearls of See also:Britain are mentioned by See also:Tacitus and by See also:Pliny; and a breastplate studded with See also:British pearls was dedicated by See also:Julius See also:Caesar to See also:Venus Genetrix. As See also:early as 1355 Scotch pearls are referred to in a See also:statute of the goldsmiths of See also:Paris; and in the reign of See also:
In Ireland the rivers of See also: Donegal, See also:Tyrone and See also:Wexford have yielded pearls. It is said that Sir See also:
The See also: Chinese also obtain marine pearls, and use a large quantity of mother-of-pearl for decorative purposes. More than twenty-two centuries before our era pearls are enumerated as a See also:tribute or tax in China; and they are mentioned as products of the western See also:part of the See also:empire in the Rh'ya, a See also:dictionary compiled earlier than moo B.C. A See also:process for promoting the artificial formation of pearls in the Chinese river-mussels was discovered by Ye-jin-yang, a native of Hoochow, in the 13th See also:century; and this process is still extensively carried on near the cityand is said to give employment to about 5000 See also:people. Large See also:numbers of the mussels are collected in May and June, and the valves of each are gently opened with a spatula to allow of the introduction of various See also:foreign bodies, which are inserted by means of a forked See also:bamboo stick. These " matrices " are generally pellets of prepared mud, but may be small bosses of See also:bone, brass or wood. After a number of these objects have been placed in convenient positions on one See also:valve, the unfortunate mollusc is turned over and the operation is repeated on the other valve. The mussels are then placed in shallow ponds connected with the canals, and are nourished by tubs of See also:night-See also:soil being thrown in from time to time. After several months, in some cases two or three years, the mussels are removed, and the pearls which have formed over the matrices are cut from the shells, while the molluscs themselves serve as See also:food. The See also:matrix is generally extracted from the pearl and the cavity filled with white See also:wax, the See also:aperture being neatly sealed up so as to render the See also:appearance of the pearl as perfect as possible. Millions of such pearls are annually sold at Soo-chow. The most curious of these Chinese pearls are those which present the form of small seated images of See also:Buddha. The figures are See also:cast in very thin See also:lead, or stamped in See also:tin, and are inserted as previously described.Specimens of these Buddha pearls in the British Museum are referred to the species Dipsas plicata. It should be mentioned that See also: Linnaeus, probably ignorant of what had long been practised in China, demonstrated the possibility of producing artificial pearls in the fresh-water mussels of See also:Sweden. See also:Pink pearls are occasionally found in the great See also:conch or See also:fountain shell of the West Indies, Strombus gigas, L.; but these, though much prized, are not nacreous, and their tint is See also:apt to fade. They are also produced by the chank shell, Turbinella scolymus, L.' Yellowish-See also:
Lyster See also:
Both are Lamellibranchs. leaves it in the form called Cercaria, which is really an immature See also: condition of the adult. The Cercaria makes its way into the tissues of a mussel and there becomes enclosed in the cyst previously described. If the mussel is then swallowed by the duck the Cercariae develop into adult Trematodes or flukes in the liver or intestines of the See also:bird. In the mussels which See also:escape being devoured the parasites cannot develop further, and they See also:die and become embedded in the nacreous deposit which forms a pearl. Dr Jameson points out that, as in other cases, pearls in Mytilus are common in certain special localities and rare elsewhere, and that the said localities are those where the parasite and its hosts are plentiful. The first See also:suggestion that the most valuable pearls obtained from pearl oysters in tropical oceans might be due to parasites was made by Kelaart in reports to the government of Ceylon in 1857-1859. Recently a special investigation of the Ceylon pearl fishery has been organized by See also:Professor Herdman. Herdman and See also:Hornell find that in the pearl oyster of Ceylon Margaritifera vulgaris, Schum, the See also:nucleus of the pearl is, in all specimens examined, the larva of a Cestode or tapeworm. This larva is of globular form and is of the type known as a cysticercus. As in the case of the mussel the larva See also:dies in its cyst and its remains are enshrined in nacreous deposit, so that, as a See also:French writer has said, the ornament associated in all ages with beauty and riches is nothing but the brilliant See also:sarcophagus of a worm. The cysticercus described by Herdman and Hornell has on the surface a See also:muscular See also:zone within which is a depression containing a papilla which can be protruded.It was at first identified as the larva of a tapeworm called Tetrarhynchus, and Professor Herdman concluded that the life-history of the pearl parasite consisted of four stages, the first being exhibited by free larvae which were taken at the surface of the sea, the second that in the pearl oyster, the third a form found in the bodies of See also: file-fishes which feed on the oysters, and the See also:fourth or adult stage living in some species of large See also:ray. It has not however been proved that the pearl parasite is a Tetrarhynchus, nor that it is connected with the free larva or the form found in the file-fish, Balistes; nor has the adult form been identified. All that is certain is that the pearls are due to the presence of a parasite which is the larva of a Cestode; all the rest is See also:probability or possibility. A French naturalist, M. Seurat, studying the pearl oyster of the Gambier Archipelago in the Pacific, found that pearl formation was due to a parasite quite similar to that described by Herdman and Hornell. This parasite was described by Professor Giard as characterized by a rostrum armed with a single terminal sucker and he did not identify it with Tetrarhynchus. Genuine See also:precious pearls and the most valuable mother-of-pearl are produced by various species and varieties of the genus Meleagrina of See also:Lamarck, for which Dr Jameson in his See also:recent revision of the species prefers the name Margaritifera. The genus is represented in tropical regions in all parts of the See also:world. It belongs to the family Aviculidae, which is allied to the Pectens or scallop shells. In this family the See also:hinge border is straight and prolonged into two auriculae; the See also:foot has a very stout byssus. Meleagrina is distinguished by the small size or See also:complete See also:absence of the posterior See also:auricula. The species are as follows.The type species is Meleagrina margaritifera, which has no See also: teeth on the hinge. See also:Geographical races are distinguished by different names in the trade. Specimens from the See also:Malay Archipelago have a dark See also:band along the margin of the nacre and are known as black-edged See also:Banda shell; those from Australia and New Guinea and the neighbouring islands of the western Pacific are called Australian and New Guinea black-See also:lip. Another variety occurs in See also:Tahiti, Gambier Islands and Eastern See also:Polynesia generally, yielding both pearls and shell. It occurs also in China, Ceylon, the Andaman Islands and the Maldives. Another form is taken at See also:Zanzibar, See also:Madagascar, and the neighbouring islands, and is called Zanzibar and Madagascar shell. Bombay shell is another See also:local form fished in the Persian Gulf and shipped via Bombay. The Red Sea variety is known as See also:Egyptian shell. Another variety occurs along the west coast of America and from Panama to See also:Vancouver, and supplies Panama shell and some pearls. A larger form, attaining a foot in See also:diameter and a See also:weight of to lb per pair of shells, is considered as a distinct species by Dr Jameson and named Margaritifera See also:maxima. It is found along the north coast of Australia and New Guinea and the Malay Archipelago. The nacreous surface of this shell is white, without the black or dark margin of the common species; it is known in the trade as the See also:silver-lip, gold-lip and by other names.It is the most valuable species of mother-of-pearl oyster. Dr Jameson distinguishes in addition to the above See also: thirty-two species of Margaritifera or Meleagrina; all these have rudimentary teeth on the hinge. The most important species is Meleagrina vulgaris, to which belong the pearl oyster of Ceylon and See also:southern India, the lingah shell of the Persian Gulf and the pearl oyster of the Red Sea. Since the opening of the See also:Suez See also:Canal the latter form has invaded the Mediterranean, specimens having been taken at Alexandria and at See also:Malta, and attempts have been made to cultivate it on the French coast. The species occurs also on the coasts of the Malay See also:Peninsula, Australia and New Guinea, where it is fished both for its shells (Australian lingah) and for pearls. Two species occur on the coasts of South See also:Africa but have no market value. Meleagrina carchariarum is the Shark's Bay shell of the See also:London market. It is taken in large quantities at Shark's Bay, Western Australia, and is of rather small value; it also yields pearls of inferior quality. The pearl oyster of Japan, known as Japan lingah, is probably a variety of Meleagrina vulgaris. Meleagrina See also:radiata is the West Indian pearl oyster. The largest and steadiest See also:consumption of mother-of-pearl is in the See also:button trade, and much is also consumed by cutlers for handles of See also:fruit and dessert knives and forks, See also:pocket-knives, &c. It is also used in the See also:inlaying of See also:Japanese and Chinese lacquers, See also:European lacquered See also:papier-mache work, trays, &c., and as an ornamental inlay generally.The See also: carving of See also:pilgrim shells and the elaboration of crucifixes and ornamental work in mother-of-pearl is a distinctive industry of the monks and other inhabitants of See also:Bethlehem. Among the South Sea Islands the shell is largely fashioned into fishing-hooks. Among shells other than those of Meleagrina margaritifera used as mother-of-pearl may be mentioned the Green See also:Ear or Ormer shell (Haliotis tuberculata) and several other species of Haliotis, besides various species of Turbo. Artificial pearls were first made in western See also:Europe in 168o by Jacquin, a See also:rosary-maker in Paris, and the trade is now largely carried on in France, Germany and See also:Italy. See also:Spheres of thin See also:glass are filled with a preparation known as " essence d'orient," made from the silvery scales of the See also:bleak or " ablette," which is caused to adhere to the inner See also:wall of the globe, and the cavity is then filled with white wax. Many See also:imitation pearls are now formed of an opaline glass of nacreous lustre, and the soft appearance of the pearl obtained by the judicious use of hydrofluoric acid. An excellent substitute for black pearl is found in the so-called " ironstone See also:jewelry," and consists of See also:close-grained See also:haematite, not too highly polished; but the great See also:density of the haematite immediately destroys the illusion. Pink pearls are imitated by turning small spheres out of the rosy part of the conch shell, or even out of pink coral. See Clements R. See also:Markham, " The Tinnevelly Pearl Fishery," in Journ. See also:Soc. Arts (1867), xv., 256; D.T. Macgowan, " Pearls and Pearl-making in China," ibid. (1854), ii. 72; F. See also: Hague, " On the Natural and Artificial See also:Production of Pearls in China," in Journ. See also:Roy. See also:Asiatic Soc. (1856), vol. xvi.; H. J. Le See also:Beck, " Pearl Fishery in the Gulf of Manar," in Asiatic Researches (1798), V. 393; K. See also:Mobius, Die echten Perlen (See also:Hamburg, 1857) ; H.Lyster Jameson, " Formation of Pearls," Proc. Zool. Soc. (1902), p1. i ; idem, " On the Identity and See also: Distribution of Mother-of-Pearl Oysters," Proc. Zool. Soc. (1901), pl. 1, pp. 372-394; Herdman and Hornell, See also:Rep. Ceylon Pearl Fisheries (London, Royal Soc., 1903) ; and Kunz and tevenson, See also:Book of the Pearl (New See also:York, 1908), with bibliography. (J. T.Additional information and CommentsThere are no comments yet for this article.
» Add information or comments to this article.
Please link directly to this article:
Highlight the code below, right click, and select "copy." Then paste it into your website, email, or other HTML. Site content, images, and layout Copyright © 2006 - Net Industries, worldwide. |
|
|
[back] PEARCE, CHARLES SPRAGUE (1851– ) |
[next] PEARL, THE |