Pearls are the secretion of nacreous material, spread, it is supposed, over some foreign substance which has been introduced into the shell, under the mantle of the mollusk. When the pearls are deposited on the shells, they generally adhere to it, when they originate in the body of the animal they are free. As a rule some foreign body is found in their centre which served as the nucleus for the deposit of the secretion. It may be a sterile egg of the animal itself, or of a fish, or a grain of sand, which was washed in.
The Chinese and other nations of the East, take advantage of this fact in natural history, for purposes of profit. They take up the living mollusk, and opening the shell introduce into it glass beads, or small metallic casts, representing some one of their gods, or other objects, and then returning the mollusk to the water, in time the animal has coated them with mother of pearl. The illustration shows a shell into which small beads have been introduced, and converted into pearls, together with a dozen small figures of Buddha, the Hindoo divinity, seated, which have been covered over with nacre also.
The pearls are at first very small, but they increase in size with the yearly deposit of a layer on the original centre. Sometimes they are diaphanous, semi-transparent, lustrous and more or less irridescent, at other times, however, they prove to be dull, obscure, and smoky even. The pearl fisheries are carried on in various places. They are found in the Persian Gulf, on the coast of Arabia, in Japan, on the shores of California, and in the islands of the South Sea. The most important ones are, however, those of the Bay of Bengal, the coast of Ceylon, and elsewhere in the Indian Ocean. Previous to 1795 most of the Indian fisheries were in the hands of the Dutch, but in 1802, after the treaty of Amiens, they passed into the possession of the English. Sometimes the Ceylon fisheries are undertaken by the Government, while at others they are sold to a contractor. In either case, before they begin, the coast is inspected by a Government official, in order to see that the banks are not exhausted by too frequent fishing.
The chief supply of mother of pearl is obtained from the fishery in the Gulf of Manaar, a large bay on the northeast of the island of Ceylon. It commences in February or March, and lasts thirty days. Some two hundred and fifty boats are engaged in it, coming for the purpose from all parts of the coast. At ten at night a gun gives the signal for them to set sail, and reaching the ground they commence as soon as the dawn affords sufficient light. Each boat carries ten rowers and ten divers, five of whom rest while the others are engaged. A negro to attend to the odd jobs and chores accompanies each boat.
PEARL FISHER IN DANGER.
The divers descend from forty to fifty feet, seventy is the utmost they can stand. Thirty seconds is the time they usually remain under water, and the best cannot stay longer than a minute and a half. When the fishing ground is reached a staging, built of the oars, is rigged to project from the boat over the water, and to the edge of this the diving-stones are hung, weighing from fifty to sixty pounds. The diver stands in a stirrup upon this, or if this is wanting upon the stone itself, holding the cord attached to it between his toes, with his left foot he holds the net for the reception of the pearl-oysters. Then, pressing his nostrils firmly with his left hand, and with his right grasping the signal cord, he is let rapidly down to the bottom. As soon as he arrives there, he removes his foot from the stone which is immediately drawn up again. Then throwing himself flat upon the ground, he hastily gathers into his net all the oysters within his reach. When he feels he must return to the surface he pulls the signal cord with a jerk, and is pulled up as quickly as possible. A good diver seeks to avoid straining himself, and so stays under water only the shortest time, seldom more than half a minute, but he will repeat the operation sometimes as much as fifteen or twenty times. The work is very distressing, the increased pressure of the water affects the entire system, and frequently on rising to the surface the water which runs from their ears, nose and mouth is tinged with blood. The effect is also to induce pulmonary diseases, and the divers rarely attain old age. Sharks are also common in these waters, and the divers are not unfrequently destroyed by these rapacious monsters, who are the more attracted by the fact that the divers, for their own convenience, are naked.
The work continues until noon, when a second gun gives notice for its cessation. The boats then return with the cargo they have gained, and are received by the proprietors on the shore, who personally superintend their discharge, which must be finished before dark, since anything left over night would most certainly be stolen.
The fisheries of Ceylon were formerly very valuable, but at present the banks show signs of exhaustion, from over-fishing most probably. In 1798 they are said to have produced nearly a million dollars' worth of pearls, but now they seldom yield more than a hundred thousand dollars' worth. The inhabitants along the coast of the Bay of Bengal, the Chinese seas, and the islands of Japan, are also engaged in the pearl fishing. Together the yield is estimated at about four millions of dollars.