Chapter 14: The Mechanism Of Diving

Diving being a profession which can be carried on in its simplest form with the simplest possible apparatus--merely a rope and a stone--its history reaches back into the dim and inexplorable past. We may well believe that the first man who explored the depths of the sea for treasure lived as long ago as the first seeker for minerals in the bosom of the earth. Even when we come to the various appliances which have been gradually developed in the course of centuries, our records are very imperfect. Alexander the Great is said to have descended in a machine which kept him dry, while he sought for fresh worlds to conquer below the waves. Aristotle mentions a device enabling men to remain some time under water. This is all the information, and a very meagre total, too, that we get from classical times.

Stepping across 1,500 years we reach the thirteenth century, about the middle of which Roger Bacon is said to have invented the diving-bell. But like some other discoveries attributed to that Middle-Age physicist, the authenticity of this rests on very slender foundations. In a book published early in the sixteenth century there appears an illustration of a diver wearing a cap or helmet, to which is attached a leather tube floated on the surface of the water by an inflated bag. This is evidently the diving dress in its crudest form; and when we read how, in 1538, two Greeks made a submarine trip under a huge inverted chamber, which kept them dry, in the presence of the great Emperor Charles V. and some 12,000 spectators, we recognise the diving-bell, now so well known.

The latter device did not reach a really practical form till 1717, when Dr. Halley, a member of the Royal Society, built a bell of wood lined with lead. The divers were supplied with air by having casks-full lowered to them as required. To quote his own words: “To supply air to this bell under water, I caused a couple of barrels of about thirty gallons each to be cased with lead, so as to sink empty, each of them having a bunghole in its lowest parts to let in the water, as the air in them condensed on their descent, and to let it out again when they were drawn up full from below. And to a hole in the uppermost parts of these barrels I fixed a leathern hose, long enough to fall below the bunghole, being kept down by a weight appended, so that the air in the upper parts of the barrels could not escape, unless the lower ends of these hose were first lifted up. The air-barrels being thus prepared, I fitted them with tackle proper to make them rise and fall alternately, after the manner of two buckets in a well; and in their descent they were directed by lines fastened to the under edge of the bell, which passed through rings on both sides of the leathern hose in each barrel, so that, sliding down by these lines, they came readily to the hand of a man, who stood on purpose to receive them, and to take up the ends of the hose into the bell. Through these hose, as soon as their ends came above the surface of the water in the barrels, all the air that was included in the upper parts of them was blown with great force into the bell, whilst the water entered at the bungholes below and filled them, and as soon as the air of one barrel had been thus received, upon a signal given that was drawn up, and at the same time the other descended, and by an alternate succession, provided air so quick and in such plenty that I myself have been one of five who have been together at the bottom, in nine to ten fathoms water, for above an hour and a half at a time, without any sort of ill-consequence, and I might have continued there so long as I pleased for anything that appeared to the contrary.” After referring to the fact that, when the sea was clear and the sun shining, he could see to read or write in the submerged bell, thanks to a glass window in it, the Doctor goes on to say: “This I take to be an invention applicable to various uses, such as fishing for pearls, diving for coral or sponges and the like, in far greater depths than has hitherto been thought possible; also for the fitting and placing of the foundations of moles, bridges, etc., in rocky bottoms, and for cleaning and scrubbing ships’ bottoms when foul, in calm weather at sea. I shall only intimate that, _by an additional contrivance_, I have found it not impracticable for a diver to go out of an engine to a good distance from it, the air being conveyed to him with a continued stream by small flexible pipes, which pipes may serve as a clue to direct him back again when he would return to the bell.”

We have italicised certain words to draw attention to the fact that Dr. Halley had invented not only the diving bell, but also the diving dress. Though he foresaw practically all the uses to which diving mechanism could be put, the absence of a means for forcing air _under pressure_ into the bell or dress greatly limited the utility of his contrivances, since the deeper they sank below the water the further would the latter rise inside them. It was left for John Smeaton, of Eddystone Lighthouse fame, to introduce the air-pump as an auxiliary, which, by making the pressure of the air inside the bell equal to that of the water outside, kept the bell quite free of water. Smeaton replaced Halley’s tub by a square, solid cast-iron box, 50 cwt. in weight, large enough to accommodate two men at a time. The modern bell is merely an enlarged edition of this type, furnished with telephones, electric lamps, and, in some cases, with a special air-lock, into which the men may pass when the bell is raised. The pressure in the air-lock is very gradually decreased after the bell has reached the surface, if work has been conducted at great depths, so that the evil effects sometimes attending a sudden change of pressure on the body may be avoided.

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.