PEARLS ; PEARL FISHERY. A pearl is a small Concretion which is formed within the hard envelope of a shell-fish. The pearl oyster nearly resembles in shape the common English oyster, but is larger, being usually about three inches in diameter. The pearls are most commonly contained in the shell ; but sometimes they are foimd in the thickest and most fleshy part of the oyster. A single oyster will frequently contain several pearls ; and it is on record that one has been known n) contain a hundred and fifty. The pearl itself is supposed to be the result of some accidental deposit or extravesation of the liquor secreted by the animal in the gradual enlargement 'Of its shell—very small in the first instance, but increased by successive layers of pearly matter.
The beautiful substance called (somewhat expressively) mother *Of pearl, is the hard silvery, brilliant internal layer of shells, es pecially oyster shells, and more particularly the pearl oyster. In English oysters this substance is too thin to be workable for manufacturing purposes ; but the oysters of the eastern seas yield it of considerable thickness. The brilliant hues which distin guish mother of pearl do not depend upon the nature of the substance, but on an ex quisitely fine series of furrows upon the sur face, which shed a brilliant refiexion of colours according to the angle afwhieh the light falls on them. Much care is.required in working this delicate substance; but it may be cut by saws, files, and drills, with the corrosive aid of sulphuric or muriatic acid. It by colcothar of vitriol. In all those orna mental manufactures where pearl is sai4 to be used for flat surfaces, such as inlaying, mosaics, buttons, knife-handles, atc.,.it is not real pearl, but mother of pearl, that is em ployed.
The Pearl Fishery, or the fishing for pearl oysters, is an important exiiploYinent on coasts ' where this particular kind of fish abounds. The chief fisheries are on the west coast of Ceylon, on the Coromandel coast, on the shores of the Persian Gulf, on the coast of Algiers, on the shares of the Sooloo Islands, flay of Panama, and pn the Pacific coast of some of the South American States'. The Ceylon fishery is a monopoly of the British govern ment; and the Coromandel fishery is a mono poly Of the East India Company ; but the rent at which the fisheries are let out seldom pays more than the expense of superintend ance. In the Persian Gulf the fishery often
yields nearly 100,0001. of pearls in two months. The oysters are procured by In the Ceylon fishery about 1200 or 1400 divers are usually employed. The share of profits gives each individual Os. to 6s. per day for the time he is employed i the price of ordinary labour being 6d. per day. But each bank being available only for one period, of about 20 days in every 7 years; sometimes the fishery is and sometimes there is none at all ; and in no season does it last for more than 30 or 35 days, commencing' with the calm weather about the 5th of March. The divers, in 0 or 7 fathoms water, remain immersed' 'from '50 to 55 seconds, very rarely longer. A reward being offered to him should longest under water, it was gained by one who remained 87 seconds. The diver's sack is not fastened round his neck, but is attached to a cord held by the man in the boat above ; and it is pulled up when full at the sign& of the diver, who, if he choose, is drawn pp with it. So far from the occupatiOn being unhealthy, it is the belief of the natives that divers live longer than other labourers ; and 'its ph* season is held as a gainful holiday by the divers themselves, who at other times are engaged in ordinary Labour. If the oyster is taken before seven years' old, its pearls are imperfectly de veloped.
When the oysters are brought to land, they are thrown into a pit 'and allowed to rot, whereby the pearls can be extracted without injury to their delicate structure. The pearls do not undergo much preparation to fit them for ornament, as an irregularly shaped pearl is as 'being but little inferior to a symmetrical one.' Various kinds of drills are employed to bore holes through the pearls ; and the pOwder of ground pearls is some times employed to polish them.
A vessel arrived at London in the early part of 1851 from Panama, with no fewer than 2,104,000 pearl shells ; to be used, we may presume, as mother of pearl. This was the largest impoilation ever known.
The mode of imitating pearls is described under pus.