Submarine Appliances And Their Uses
Deep Sea Diving, &c., &c.

I fie 6-bolt helmet has two metal bands, the under side of each having- three recesses into which corresponding ribs formed on the indiarubber collar of diving dress fit. 1 he 3-BOLT helmet has a flanged ring at the lower end of the head-piece and another on the breastplate, to correspond, each being formed with three lugs spaced equi-distant, the lugs of the breastplate being fitted with metal bolts, the lugs of the upper ring having holes to correspond. The indiarubber collar of diving dress has a similar flange, which is clamped between the metal rings above described, the whole being secured watertightly with three metal nuts. I he 2-BOLT helmet is fitted with a metal clamping piece, back and front of which is fitted a bolt. I he diver having put on his diving dress, the clamping piece is placed under the indiarubber collar, just inside the bead formed on the edge of the latter. I he corselet, which is formed with the helmet in one piece (the former having a hole back and front, corresponding with the two bolts in the clamping piece), is put over the bolts, and the whole is then screwed up with the two nuts provided, the clamp- ing' piece and corselet, with the rubber collar between, thus being drawn together and making a watertight joint. I he clamping piece is strengthened from the back and front towards the shoulders, so that there is no fear of its buckling. Lock Helmet (two forms) :—(a) has a ring, formed with a nipple, on the lower part of the head-piece, and a recessed ring, in which is fitted a rubber washer, on the breastplate. I he rubber collar of the diving dress is formed with a flange which fits into the recessed ring described ; the head-piece, which is hinged on to the back of the breastplate, is then closed clown on to the rubber collar (the nipple of the upper ring entering the orifice of the breastplate and pressing against the inner side of the rubber collar), the whole being clamped securely with a special locking device. (&) is somewhat similar in principle to the helmet described above (a), except- ing that in the present case the joint between helmet and dress is made by screwing the head-piece to the breastplate, the flange of the rubber collar of the dress fitting in a recess in the breast-plate. The air-inlet connections of all these helmets are fitted with non-return valves, which, together with the regulating outlet valves, are described on pages 25, 26 and 27. The Regulating Outlet Valves - are of four types, each of which, when ad- justed, works automatically. Those lettered A. B. and D. are regulated by hand. When it is desired to let air escape the screw is turned outwards ; when it is required to retain more air in the dress the screw is turned inwards. 24