22. To collect the shells containing these singular productions, is the business of _divers_, who have been brought up to this dangerous occupation. They must generally descend from eight to twelve fathoms, and must remain beneath the surface of the water for several minutes, during which time they are exposed to the attacks of the voracious shark. In addition to the danger from this cause, the employment is very destructive of health. 23. In preparing a diver for his descent, a rope is tied round the body, and a stone, weighing twenty or thirty pounds, is fastened to the foot to sink him. His ears and nostrils are filled with cotton, and a sponge dipped in oil is fastened to his arm, to which he may now and then apply his mouth, in order to breathe without inhaling water. In addition to these equipments, he is furnished with a knife, with which the shells may be detached from the rocks, and with a net or basket, in which they may be deposited. 24. Thus equipped, he descends to the bottom, and having filled his depository, or having stayed below as long as he may be able, he unlooses the stone, gives the signal to his companions above, who quickly draw him into the boat. At some pearl-fisheries, the diving-bell is employed, which in some degree obviates some of the dangers before stated. 25. The shells thus obtained are laid by, until the body of the animal has putrified, when they commonly open of themselves. Those which contain any pearls, generally have from eight to twelve. The pearls having been dried, are assorted according to their various magnitudes; and, to effect this separation, they are passed through nine sieves of different degrees of fineness. The largest pearls are about the size of a small walnut; but such are very rare. The smallest are called _seed pearls_. 26. Pearls are of various colors, such as white, yellow, lead-color, blackish, and totally black. The "white water" is preferred in Europe, and the "yellow water," in Arabia and India. In regard to their form, they vary considerably, being round, pear-formed, onion-formed, and irregular. The inner part of the pearl muscle is called _nacre_ or _mother of pearl_, and this is manufactured into beads, snuff-boxes, spoons, and a variety of other articles. 27. Pearls were objects of luxury among the ancients. A pearl valued by Pliny at a certain sum, which, reduced to our currency, amounts to $375,000, was dissolved by Cleopatra, and drunk to the health of Antony, at a banquet. These beautiful productions are not estimated so highly at present. The largest will sometimes command four or five hundred dollars, although very few, which are worth over forty or fifty dollars, are ever brought to this country.