Pearl is a hard, white, shining body, usually roundish, found in a testaceous fish, resembling an oyster; and, although an animal production, it is usually ranked among the number of gems or precious stones. The fish wherein the pearls are found is three times the size of the common oysters ; and is called by naturalists, Mytilus mar-garitiferus or pearl muscle. Each muscle commonly yields ten or twelve pearls, though an hundred and fifty, it is pretended, have been seen in the same fish. Some among them are much larger than others and ripen faster. The most perfect drop first, the rest remaining at the bottom of the shell. Some grow so big as to hinder the oyster from shutting, in which case the fish rots and dies. The formation of pearls has embarrassed both ancient and modern naturalists. Pliny Supposes them formed of the dew. "The fish," says he, "rises every morning to the surface of the water, and there opens its shell to imbibe the dew of the heavens, as some liquors are converted into crystals in the earth; or as the juice of flowers into honey and wax in the body of the bee, so the dew, like a liquid pearl, insinuating into the body of the fish, fixes its salts, and there assumes the colour, hardness, and form of pearl." But this, how plausible soever, is false; for the pearl muscles adhere to the bottom of the sea, and nobody ever yet saw any of them appear on the surface of the water. Some think pearls to be the eggs of the fishes they are found in; but neither does this agree with the phenomena; for pearls are found throughout the whole sub-stanceof the oyster - in the head, the coat that covers it, the circular muscles that terminate it, the stomach, and other parts. M. Reaumur observes that pearls are formed like other stones in animals, as those in the bladder, kidneys, etc. ; that they are apparently the effects of a disease in the fish; that they are formed of a juice extravasated out of some broken vessels, and detrined and fixed in the membranes. The shells of sea fishes, as well as those of snails, etc, are formed of a glutinous, calcareous matter, oozing out of the body of the animal; and it is no wonder that an animal which has vessels wherein circulates a sufficient quantity of matter (albumen and carbonate of lime) to build, thicken, and extend a shell, shall have enough to form stones, if this matter should happen to overflow and burst forth into any cavity of the body, or among the membranes.
Pearls are caught, in the seas of the East Indies - on the coast of Persia, near Ormuz - about Cape Comorin, and on the coast of the Island of Ceylon. They are caught also in the American Seas, and in some parts of Europe - as on the coast of Scotland, and in a river of Bavaria. At the commencement of the season, which is in March and April, and again in August and September, there appear frequently two hundred and fifty barks on the pearl banks : in the larger are two divers, in the smaller, one. Each bark puts off from shore before sunrise, by a land breeze which never fails, and returns again by a sea breeze which succeeds at noon. As soon as the barks are arrived at the place where the fish lie, and have cast anchor, each diver binds a stone under his body, which is to serve him as ballast, and prevent his being driven away by the motion of the waters, and also to enable him to walk more steadily among the waves; besides this, they tie another heavy stone to one foot, in order to sink them to the bottom of the sea; and as the oysters adhere strongly to the rocks, they arm their fingers with leathern gloves, or take an iron rake to displace them with Lastly, each diver carries with him a large net, tied to his neck by a long cord, the other end of which is fastened to the side of the bark. The net or sack is intended to hold the oysters he may collect, and the cord is to pull him up by when his bag is full, or when he wants air. Thus equipped, he precipitates himself sometimes above sixty feet underwater. As soon as he arrives at the bottom he begins to tear the oysters from the rock, and thrust them into his budget. At whatever depth the divers are, the light is sufficient for them to see what passes around them, and sometimes, to their great consternation, they behold monstrous fishes, from whose jaws they can escape only by muddying the water, and concealing themselves by that means; although the artifice will not always save them from falling a prey to their formidable enemies.
The best divers, it is said, will remain under water near a quarter of an hour, during which time they will hold their breath without the use of oils, acquiring the habit by long practice; but the exertion is so violent, as generally to shorten the lives of those who repeat it frequently.