The armored divers are mostly white sailors, Germans, Swedes, a few English, and an occasional American; and so great is the advantage of the diving suit that one armored diver is considered equal to a whole crew of natives. Instead of a swift, breathless struggle of fifty or sixty seconds, at a depth of fifty feet or less, with a limit of seventy-five, the armored diver can work for ten minutes at a depth of a hundred feet, while at a depth of thirty he can work for a couple of hours. The deep-sea dangers to which the naked diver is exposed are mostly shared by the armored diver. The protection from the tremendous crushing pressure of the water afforded by the suit and the cushion of inclosed air is offset by the increased pressure at greater depths. The armored diver likewise encounters the venomous stonefish. This little fish punctures the hand reaching for a shell and injects a poison which causes the whole arm to swell, with great pain. The remedy is to remain down, as the pressure of water induces free bleeding at the wound, and the consequent outflow of the poison. If the bitten diver comes to the surface, as the unarmored diver must, the arm swells rapidly, turns black, and is painful for weeks.
Sharks do not attack the armored diver, but he has peculiar perils which the naked native diver escapes. At some great depth the air-pump may not work, or the air-pipe may burst. But there are greater dangers yet. Pearl oysters are not found in beds, like our edible bivalves, but scattered over the sea bottom; hence it is the custom to beat up against the tide or current, and then let the lugger drift, with a drag-anchor perhaps. Yet sometimes the drifting boat is seized by a strong current and whirled along, and then, while the diver hurries on to keep up, his life-line or air-pipe may become fatally entangled in branching coral; or, again, a slack line or pipe may fall into the jaws of the "giant clam," which close over it, and hold the diver prisoner to his death, alone in the dim ocean depths.
The most perfect pearls are found within what is called "the mantle" of the mollusk, an elastic membrane which envelops the oyster, and which is supposed to secrete the nacreous fluid. The finest specimens lie near the lips of the shell, or are imbedded in the softer part of the oyster near the hinge of the shell. The ideal gem pearl is spherical, white, without blemish in texture or "skin," with pure "water" or appearance of transparency—though no pearl is really transparent—and of distinguished lustre or orient. Lustre is the soul of the pearl, as brilliancy is of the diamond. Finely formed drop shapes, and then oval or egg shapes, are but little below the spherical pearls in value, if of equal perfection. The fine gem pearls are the size of peas; very much larger specimens, of twenty-five grains and upward, of perfect quality, are rare, and command corresponding values.