There are now two general types of deep-sea diving equipment: an India rubber dress, covering the entire body, except the head, which is covered by a helmet, and another apparatus which is constructed entirely of metal.

The India rubber dress has a neck-piece or breast-plate, fitted with a segmental screw bayonet joint, to which the head-piece or helmet, the neck of which has a corresponding screw, can be attached or removed. The helmet has usually three eyeholes, covered with strong glass, and protected by guards. Air is supplied by means of a flexible tube which enters the helmet and communicates with an air pump above. To allow of the escape of the used air there is sometimes another flexible tube, which is led from the back part of the helmet to the surface of the water. But in the more improved forms of the dress, the breathed air escapes by a valve so constructed as to prevent water from getting in, though it lets the air out. Leaden weights are attached to the diver, and his shoes are weighted, that he may be able to descend a ladder, walk about below, etc.

Communication can be carried on with those above by means of a cord running between the diver and the attendants; or he may converse with them through a speaking tube or a telephonic apparatus. One form of diving-dress makes the diver independent of any connection with persons above the water. It is elastic and hermetically closed. A reservoir containing highly compressed air is fixed on the diver's back, which supplies him with air by a self-regulating apparatus at a pressure corresponding to his depth. When he wishes to ascend he simply inflates his dress from the reservoir.

Another form, known as the Fleuss dress, makes the diver also independent of exterior aid. The helmet contains a supply of compressed oxygen, and the exhaled breath is passed through a filter in the breast-piece which deprives it of its carbonic acid, while the nitrogen goes back into the helmet to be mixed with the oxygen, the supply of which is under the diver's own control, and to be successively breathed. A diver has remained an hour and a half under thirty-five feet of water in this suit.

A considerable enlargement of the field of deep-sea diving is the result of the invention recently of a form of diving apparatus which is unaffected by the limitations hitherto imposed on work of this kind. A possible depth of 204 feet is recognized by the British Admiralty regulations under the conditions that obtain with the common form of diving suit. Yet this depth has probably never been reached. One hundred feet is the rare descent of the average diver and 150 feet his maximum. With the new apparatus a submergence of 212 feet has been obtained, and this might have been indefinitely extended had there been a greater depth of water at the place where the experiment took place - Long Island Sound during the latter part of 1914.

The new diving apparatus is constructed entirely of metal, is rigid and is made of such materials that it is strong enough to resist the great pressures found in the depths to which it can penetrate. The material used is an alloy of aluminum, and the diving case weighs complete about 500 pounds. When in the air, the man inclosed in it is incapable of imparting movement to it, but in the water, which counterbalances the dead weight of the apparatus, he can easily move the articulated sections as well as give himself motion through the water. The articulated portion consists of about fifty turning joints, fitted with leather packing, which swells and has an increased effectiveness under increased water pressure. To prevent the pressure-force of the deep sea from jamming the joints, roller bearings are so arranged about them that freedom of action is constantly maintained.

Diving-Dress and Diving-Helmet, by Siebe, Gorman & Co..

A. Pipe by which air is supplied. B. Vaive by which it escapes.

The diving case is not absolutely water-tight, nor is it desired that it should be so, as the slight leakage acts as a lubricant to the joints, and aids in their movements. The danger arising from the intake of water thus into the diving case is averted by the action of an ingenious pump appliance, which serves two purposes: that of pumping the water out and pumping the air in. The diver in this invention carries his pump with him and has air supplied to him at atmospheric pressure.

At the back of the diving case is a recess and in it is installed a compact but powerful pump, which sucks from the feet of the suit all leakage and forces it at once outward. This pump is worked by compressed air, and the air, after performing its mechanical part of driving the pump, is exhausted into the suit for the diver to breathe and then passes to the surface through the free space in an armored rubber tube, within which are led down to the diver the compressed air pipe for driving the pump, and the electrical connections for telephone and lamp. Thus the diving case receives a thorough ventilation, and it has been found that should the pump fail to work for a number of minutes there would still be enough air remaining in the diving case and the tube space to supply the diver's needs for at least the length of time he is being hauled to the surface.

During the experiment in Long Island Sound the pump was stopped for ten minutes, while the diver was at a depth of 100 feet. He suffered no inconvenience, and when the compressor again was started he was lowered to a depth of 212 feet. If such a condition as failure of the pump to work for ten minutes had arisen during a descent in the old elastic diving dress the result must necessarily have been fatal. Nor is a delay necessary in hoisting the diver clad in the new diving apparatus to the surface. According to the British Admiralty regulations, should a diver go down to a depth of 204 feet, the time of his ascent must be not less than one hour and a half. In the Long Island Sound experiments the diver was hoisted to the surface in eighty-seven seconds. He was totally uneffected by the abrupt change in pressure, although the deepest he had ever been was ninety feet, and on that occasion he had suffered from bleeding at the nose and fears.