A Treatise On The Principles And Practice Of Harbour Engineering

56 HARBOUR ENGINEERING. so as to prevent thé condensation of the diver’s breath upon them. The other fittings of a helmet are the inlet and outlet valves of the air supply, the latter of which is equipped with a regulator, so that the diver can control his supply of air to a nicety. The inlet valve is so constructed that air is allowed to enter freely, but cannot possibly escape that way, and, in the event of damage occurring to the supply pipe, by closing the outlet valve, the apparatus would retain sufficient air to enable the diver to return to the surface. The dress is in one complète piece, made of solid sheet india-rubber between double-tanned twill. It is fitted with vulcanised india-rubber cuffs and collar, the former being sufficiently close fitting to the wrists to prevent the entrance of water, and the latter pierced with holes to correspond with the damping screws of the breastplate. In English practice the number of these holes is about a dozen; in French practice, three. The cuffs have generally to be expanded with metal expanders, shaped like shoe-horns, to admit of the passage of the hands, but, in some cases, a bead is moulded on the edge of the cuff, which enables it to be rolled back over the hands. Should the cuffs not prove sufficiently water-tight, the writer has found it a good plan to bind the wrists with a band of moistened chamois leather before the cuffs are put in place. As it is no uncommon occurrence for a little water to enter the dress through leakage, or occasionally through allowing the outlet valve to be open rather too widely, the diver, before putting on the dress, removes his outer garments and dons a guernsey, drawers, and stockings, as protection from wet and also as padding to his body. For deep or cold water these habiliments may be doubled or trebled. He wears a pair of canvas socks over the feet of the dress to protect it when walking about without shoes, and, if his work is likely to lead him into rough and rocky places, an outer suit of canvas overalls is désirable. The boots are strapped on at the last moment before descending. They are either of specially stout leather, heavily shod with lead, or cast in brass with leather uppers. Additional weight is generally provided for the body of the dress by loading the breast and back with lead pads slung across the shoulders. The diver’s personal equipment is completed by a leather waist-belt containing a knife in a sheath. India-rubber gauntlets may be added, but in this country most divers work without them. The air-pipe is made of the best india-rubber hose with a core of either hardened steel wire, tinned to prevent rusting, or of brass or copper wire. The pipe may be made to float or sink by adjusting the weight of metal. It should be tested to a pressure of 200 or 300 Ibs. per square inch. After being screwed up to the helmet, the pipe is led and secured under the diver’s left arm, so as to be conveniently at his command, and thence it passes upward to the pump. A life-line of stout cord is fastened round the diver’s body. Both life-line and air-pipe are paid out together through the hands