Diving bells are very useful for laying submarine masonry, usually consisting of huge stone blocks set in hydraulic cement. Helmet divers explore and prepare the surface on which the blocks are to be placed. Then the bell, slung either from a crane on the masonry already built above water-level, or from a specially fitted barge, comes into action. The block is lowered by its own crane on to the bottom. The bell descends upon it and the crew seize it with tackle suspended inside the bell. Instructions are sent up as to the direction in which the bell should be moved with its burden, and as soon as the exact spot has been reached the signal for lowering is given, and the stone settles on to the cement laid ready for it.
The modern diver is not sent out from a bell, but has his separate and independent apparatus. The first practical diving helmet was that of Kleingert, a German. This enclosed the diver as far as the waist, and constituted a small diving bell, since the bottom was open for the escape of vitiated air. Twenty years later, or just a century after the invention of Halley's bell, Augustus Siebe, the founder of the present great London firm of Siebe, Gorman, and Company, produced a more convenient "open" dress, consisting of a copper helmet and shoulder-plate in one piece, attached to a waterproof jacket reaching to the hips.
The disadvantage of the open dress was, that the diver had to maintain an almost upright position, or the water would have invaded his helmet. Mr. Siebe therefore added a necessary improvement, and extended the dress to the feet, giving his diver a "close" protection from the water.
We may pass over the gradual development of the "close" dress and glance at the most up-to-date equipment in which the "toilers of the deep" explore the bed of Old Ocean.
The dress—legging, body, and sleeves—is all in one piece, with a large-enough opening at the shoulders for the body to pass through. The helmet, with front and side windows, is attached by a "bayonet joint" to the shoulder-plate, itself made fast to the upper edge of the dress by screws which press a metal ring against the lower edge of the plate so as to pinch the edge of the dress.
Photo Cribb.
THE DIVER AT WORK
Note the telephone attachment, the wires of which are embedded in the life-line held by the bluejacket on the left. By means of the telephone the diver can give and receive full instructions about his work.
At the back are an inlet and an outlet valve. Between the front and a side window is the transmitter of a loud-sounding telephone, and in the crown the receiver and the button of an electric bell. The telephone wires, and also the wires for a powerful electric light, working on a ball-and-socket joint in front of the dress, are embedded into the life-line. The air-tube, of canvas and rubber, has a stiffening of wire to prevent its being throttled on coming into contact with any object. A pair of weighted boots, each scaling 17 lbs., two 40-lb. lead weights slung over the shoulder, and a knife worn at the waist-belt, complete the outfit of the diver, which, not including the several layers of underclothing necessary to exclude the cold found at great depths, totals nearly 140 lbs. Of this the copper helmet accounts for 36 lbs.