DIVING. The art of descending in water. Independently of the valuable native productions which are found at the bottom of the sea, such as pearls, coral, sponges, &e., the treasure which is so frequently carried down in wrecked vessels makes it an object of importance to be able to descend to the bottom and remain there long enough to execute the operations necessary to recover it. But without the assistance of some mediani cal apparatus, it is extremely little that even the most practised divers can per form. A minute and a half, or two minutes, is the longest time that a diver, in general, can remain under water. Be sides, on account of the loss of in water, the power which a man can exert is extremely small, unless borne down by a load which would entirely prevent him from rising again to the top. For these reasons, numerous projects have been brought forward to assist the natural powers of the body, and render diving an art of more extensive utility. In all these projects, the principal object aimed at is to supply the diver with fresh air and light, and leave him the free use of his arms, and the power of walking within a moderate range at the bottom. Borelli contrived an apparatus which he called a diving bladder ; the bladder be ing of brass or copper, about two feet in diameter, to contain the diver's head, and fastened to a goat-skin covering ex actly fitted to the shape of the head. An apparatus of this kind was successfully used by Mr. Deane on the west coast of Scotland, at Spithead, and at Donagha dee, where he brought up an immense number of dollars and various other ar ticles from a vessel which had been wrecked there more than thirty years before.
The principal part of Mr. Deane's ap paratus consists of a helmet of thin sheet copper, which covers the head of the diver, large enough to admit of free mo tion, and furnished with three eve-holes, covered with glass protected by brass wires. The helmet comes pretty well
down over the breast and back, and is fastened by rivets to a waterproof can vass jacket so tightly that no water can penetrate. A leather belt passes round the diver, to which are attached two weights, one before and the other be hind, each about 40 lbs. The belt is supplied with a buckle in front, which, in case of any accident happening, can be instantly undone. The diver is sup plied with fresh air by means of a flexi ble water-proof pipe, which enters the helmet, and communi cates with an air-pump, wrought above in the barge from which he de scends. This pipe pas ses under the left arm of the diver, and enters the back of the helmet, being so contrived that the fresh sir is made to impinge on the glasses ; which in a great measure prevents their being dimmed by the moisture of the breath. From the back part of the helmet there is also led en eduction pipe, to allow the escape of the breathed air. A single line passes under the right arm to communicate with attendants at the surface. The diver descends from the side of the ves sel, either by means of a rope or wooden ladder, loaded at the lower end, the weight being kept at a little height above the ground. When the diver descends to the bottom, the weight is let down, and the rope allowed to become slack, to prevent the motion of the boat from ob structing him. His motion is rendered steady by heavy weights attached to his feet : and he carries a line in his hand, that he may, when necessary, guide him self back to the rope. A waterproof dress covers his body entirely ; and he is thus enabled to remain under water five ' or six hours at once, all the while per fectly dry.