PEARL, a peculiar product of certain Marine and fresh water mollusks or shell-fish. Most of the molluscous animals which are aquatic and reside in shells are provided with a fluid secretion with which they line their shells, and give to the otherwise harsh gran ular material, of which the shell is formed. a beautifully smooth surface, which prevents any unpleasant friction upon the extremely tender body of the animal. This secretion is evidently laid in extremely thin semi-transparent films, which, in consequence of such an arrangement, have generally a beautiful iridescence, and form in some species a suffi cient thickness to be cut into useful and ornamental articles. The material itself in its hardened condition is called nacre by zoologists, and by dealers, mother-of-pearl (q.v.). Besides the pearly lining of the shells, detached or generaVy spherical or rounded por tions of time nacre are often found on opening the shells, and there is great reason to sup pose these are the result of accidental causes„ such as the intrusion of a grain of sand or other substance, which by irritating the tender body of the animal, obliges it in self. defense to cover the cause of offense, which it has no power to remove; and as the secre tion goes on regularly to supply the growth -and wear of the shell, the included body constantly gets its share, and thereby continues to increase in size until it becomes a pearl. The Chinese avail themselves of the knowledge of this fact to compel one spe. cies of fresh water mussel, unio kgria, to produce pearls. In order to do this, they keep the uuios in tanks, and insert between thc, shell and the mantle of the animal either small leaden shot or little spherical pieces of mother-of-pearl. These arc sure to receive regular coatings of the nacreous secretion; and after a time look -like pearls formed under ordinary circumstances. These curious people also practice another trick upon these animals; they insert small images of the Buddha stamped out of metal, which soon become coated with the pearl secretion, and are cemented by 'it to the shells; to those ignorant of its origin, the phenomenon is a supernatural testimony to the truth of Buddhism. Examples of these curosities are to be found in many of our museums.
A plan of making pearls was suggested to the Swedish government by Linnaeus. It consisted iu boring a small hole through the shell of the river mussel, and inserting a grain of sand, so as to afford -a nucleus for a pearl. The plan at first succeeded suffi ciently well to prove its practicability, and he was rewarded by a sum of money (S450), but it failed as a profitable speculation, and was abandoned.
The exact nature of the secretion has never been satisfactorily determined; it is, how ever, ascertained that it is deposited in thin films, which overlie each other so irregularly that when magnified they present the appearance of sharply serrated edges, and to this peculiar dispositiou of the plates, thebeautiful iridescence of pearls is attributed. Their formation was a great puzzle to the ancients, amongst whom they were very highly prized. Dioscorides and Pliny mention the belief that they were drops of dew or rain which fell into the shells when opened by the animal, and were then altered by some power of the animal into pears. This opinion, which obtained all over the east, is thus charmingly alluded to by Moore: The most famous pearls are those from the east; the coast of Ceylon, or Taprobane, as it is called by the Greeks, having from the earliest times been the chief locality for pearl fishing. They are, however, obtained now of nearly the same quality in other parts of the world, as Panama in South America, St. _Margarita in the West Indies, the Coroman del coast, the shores of the Sooloo islands, the Bahrein islands, and the islands of Karak and Corgo in the Persian gulf. The pearls of the Bahrein fishery are said to lie even finer than those of Ceylon, and they form an important part of the trade of Bassora. These, and indeed all the foreign pearls used in jewelry, are produced by the pearl oyster (q:v.). The shells of the mollusks which yield the Ceylon, Indian, and Persian
ones, are sometimes as much as a foot in diameter, and are usually about nine inches. Those of the new world, although the shells are smaller and thicker, are believed to be the same species. The chief locality of the Ceylon pearl fishery is a hank about 20 m. long, 10 or 12 m. from shore, .opposite to the villages of Condatelly and Arippo on the northern coast. The season of the fishery lasts about three months, commencing at' the beginning of February, and is carried on under government regulations. The boats employed are open, and vary in size from 10 to 15 tons burden; they put out at night, usually at 10 o'clock, on a signal gun being fired from the fort of Arippo, and make for the government-goard vessel, which is moored along the bank, and serves the double purpose of a guard and a light-ship. The divers are under the direction of a manager, who is called the adapanaar, and they are chiefly Tamils and Moors from India. For each diver there is provided a diving-stone, weighing about 30 pounds, which is fastened to the end of a rope long enough to reach the bottom, and having a loop made for the man's foot; and in addition to this, a large net-work basket, in which to place the pearl oysters as lie collects them. These are hung over the sides of the boat; and the direr, placing his foot in the loop attached to the stone, liberates the coils of the rope, and with his net-basket rapidly descends to the bottom. To each boat there is usually allotted a crew of 13 men and 10 divers, five of whom are descending whilst .the others are resting. This work is done very rapidly; for, notwithstanding the stories to the contrary, the best divers cannot remain longer than 80 seconds below, and few are able to exceed CO. The greatest depth they descend is 13 fathoms, and usual depth about 0 fathoms. When the diver gives the signal by pulling the rope, lie is quickly hauled up with his net and its contents. Accidents rarely happen; and as the Then are very superstitious, their safety is attributed to the incantations of their Aa•k-charmers, performed at the com mencement. of the fishing. Sir E. Tennent, however. attributes the rarity of accidents from sharks, usually so abundant in tropical seas, to the bustle and to the excitement of the waters during the fishery frightening away those dreaded creatures. The divers are sometimes paid fixed wages. others agree for one-fourth of the produce. When a boat-load of oysters has been obtained, it returns to shore, and the cargo, sometimes amounting to 20.000 or 30.000. is landed and piled on the shore to die and putrefy, in order that the pearls may be easily found. The heaps are formed in small walled compartments, the walls surrounding each being about one or two ft. in height. Several of these compart ments surround a small central inclosure, in which is a bath, and they slope toward this bath,. and are each connected with it by a small channel, so that any pearls washed out from the putrefying mass by the rain may be carried into the bath. When the animals in the shells are sufficiently decomposed, the washing commences, and great care is taken to watch for the loose pearls, which are always by far the most valuable; the shells and then examined, and if any attached pearls are seen, they are handed over to the clippers, 'who, with pinchers or hammer, skillfully remove them. Such pearls are used for setting;• whilst the former, being usually quite round, are drilled and strung, and can be used for beads, etc. The workmen who are epployed to drill the pearls also round the irregular ones, and polish them with great slal. The method of holding the pearls dur ing these operations is very curious; they make a number of holes of sinhli depth in a piece of dry wood, and into these they fit the pearls, so that they are only partly below the surface of the wood, which they then place iu water, As it soaks up the water and swells, the pearls become tightly fixed, and are then perforated, etc. These operations arc all carried ou on the spot.