DIVING-BELL. 



DIVING-BELL. 



682 



of the water ; and to a figure published in a work on fortification, by 

 Lorini. in 1607, which nearly resembles the modern diving-bell. Beck- 

 niann considers the insertion of the former as a proof that the person 

 who drew them was not acquainted with the diving-bell, which he 

 would otherwise have delineated. The machine described by Lorini 

 consists of " a square box bound round with iron, which is furnished 

 with windows, and has a stool affixed to it for the diver." Lorini, 

 who was an Italian, does not lay claim to the invention of this 

 apparatus. 



Dr. Halley, in No. 349 of the ' Philosophical Transactions,' (vol. 

 xxix.) describes the defects of the diving-bell, asl previously used, 

 and suggests a remedy for them. This paper alone would be sufficient, 

 although it does not enter into the early history of the machine, to 

 contradict the erroneous statement which has been made to the effect 

 that Halley was the inventor of the diving-bell. 



In its simplest form the diving-bell is a strong heavy vessel of wood 

 or metal, made perfectly air and water tight at the top and sides, but 

 open at the bottom. If such a vessel be gradually lowered into the 

 water, in a perfectly horizontal position, the air which it contains can- 

 not escape, and therefore the vessel cannot become full of water. 

 This may be readily illustrated by plunging a glass tumbler, in an 

 inverted position, into a vessel of water, and placing a bit of cork, or 

 any other substance which will float, on the surface of the water, under 

 the glass. If a bit of burning matter be laid upon the cork-float, it 

 will be seen that it continues burning, although the glass and all 

 that it contains be plunged far beneath the water ; thereby proving 

 that the upper part of the cavity of the glass is occupied by air, and 

 not by water. In this experiment, however, it will be observed that 

 the water does fill a small part of the cavity of the glass, and that it 

 rises more into it when it is plunged to a considerable depth than when 

 the rim is only just immersed beneath the surface. This is occasioned 

 by the condensation of the ah- contained in the glass, which being very 

 elastic and compressible, is condensed into a smaller space by the pres- 

 sure of the superincumbent water, when the glass is plunged to a con- 

 siderable depth, than it will occupy under the ordinary pressure of the 

 atmosphere. Where the diving-bell is used for descending to a very 

 small depth, as the pressure of the water is email, it will not rise in 

 the bell to a sufficient height to be inconvenient ; but at the depth of 

 83 feet the pressure is so great as to compress the air into one-half its 

 original rolume, so that the bell will become half full of water; and 

 at a greater depth the air will be still more compressed, and the water 

 will rise proportionately higher in the bell. This condensation of the 

 air does not materially interfere with respiration, provided the descent 

 of the bell be very gradual, as the air then insinuates itself into the 

 cavities of the body and balances the pressure from without. The 

 principal effect of the increased pressure is a pain in the ears, occa- 

 sioned by the circumstance that the Eustachian tube does not allow 

 the condensed air immediately to find its way into the cavities of the 

 ear, so that the pressure on the outside of the tympanum is, for a time, 

 unbalanced by a corresponding pressure from within, and occasions 

 a sensation like that of having quills forced into the ears. This con- 

 tinues until the pressure of the air hi the mouth, which at first has a 

 tendency to keep the aperture of the Eustachian tube closed, forces it 

 open ; an action which is accompanied by a noise like a slight explosion. 

 The condensed air then enters the interior cavities of the ear, and, by 

 restoring the equilibrium of pressure on each side of the tympanum, 

 removes the pain ; which will return, and be remedied in the same 

 manner, if the bell should descend to a greater depth. But while the 

 mere condensation of the air in the bell does not render it unfit for 

 respiration, it would soon become so if no means were provided for 

 renewing it from time to time, as it becomes vitiated by repeated 

 respiration. The improvements invented by Dr. Halley provided a 

 remedy for this inconvenience, and for that of the contracted space 

 left free from water, when, by being at a great depth, the air is com- 

 pressed into a small volume, by affording a convenient means of 

 supplying the bell with any required quantity of fresh air, without 

 raising it to the surface. 



The bell used by Dr. Halley was of wood, in the form of a truncated 

 cone, 5 feet in diameter at the bottom, and three feet at the top, and 

 containing about sixty cubic feet. This was coated with lead, and so 

 weighted about the lower part that it would sink while empty, and 

 would always remain in ita proper position ; that is, with the large open 

 end downwards, with its rim parallel with the horizon. In the top of 

 the bell was a very strong glass window, and a cock, by opening which 

 the foul air might be allowed to escape. About a yard below the 

 mouth of the bell was suspended a stage, so weighted that it might 

 hang steadily. The whole apparatus was suspended from a sprit 

 attached to the mast of a ship, and provided with tackle by which the 

 bell might be raised or lowered, and the sprit might be slung round so 

 as either to carry the bell over the hull of the vessel, or to suspend it 

 clear of her side. The apparatus for conveying air to the diving-bell 

 consisted of two barrels, holding thirty-six gallons each, weighted with 

 lead to make them sink readily. Each of these had an open bung-hole 

 in the lower end, to allow water to enter during their descent, so as to 

 condense the air in the manner described when explaining the principles 

 of the diving-bell itself. There was also a hole in the upper end of 

 each, to which was fitted an air-tight leathern hose, long enough to fall 

 below the bottom of the barrel, and having its loose end 80 weighted 



that it would fall naturally into that position. These air-barrels were 

 attached to tackle, by which, with the easy labour of two men, they 

 might be made to rise and fall alternately, like two buckets in a well ; 

 and, by lines attached to the lower edge of the bell, they were so 

 guided in their descent that the mouth of the hose always came directly 

 to the hand of a man who stood upon the stage suspended from it. 

 As the apertures of the hose were, during their descent, always below 

 the level of the barrels, no air could escape from them ; but when they 

 were turned up by the attendant, so as to be above the level of the 

 water in the barrels, the air rushed out with great force into the bell, 

 the barrels becoming at the same time full of water. By sending 

 down these air-barrels in rapid succession, the air in the barrel was 

 kept in so pure a state that five persons remained in the bell, at a 

 depth of nine or ten fathoms, for more than an hour and a half at a 

 time, without injurious consequences ; and Halley states that he could 

 have remained there as long as he pleased, for anything that appeared 

 to the contrary. In addition to this, by the copious supply of air 

 admitted during the descent, the bell was kept constantly full of ah-, 

 and the water was prevented from entering to any inconvenient extent. 

 Halley observed that it was necessary to be let down gradually at first, 

 and to pause at the depth of about twelve feet, to drive out, by the 

 admission of a supply of air, the water which had entered the bell. 

 When the diving-bell was arrived at the required depth, he let out, by 

 the cock in the top of the bell, a quantity of hot impure air, equal to 

 the quantity of fresh air admitted from the barrels. This foul air 

 rushed up from the valve with such force as to cover the surface of 

 the sea with a white foam. So perfect was the action of this apparatus, 

 that Halley says he could, by removing the hanging stage, lay the 

 bottom of the sea so far dry, within the circuit of the bell, as not to be 

 over shoes thereon. When the sea was clear, and especially when the 

 sun shone, sufficient light was transmitted to allow a person in the 

 bell to write or read ; and when the sea was troubled and thick, which 

 occasioned the bell to be as dark as night, a candle was burnt in it. 

 Halley sometimes sent up orders with the empty air-barrels, writing 

 them with an iron pen on plates of lead. Having, by these ingenious 

 contrivances, removed the principal difficulties attending the use of the 

 diving-bell, Halley foresaw its extensive xitility. He observes, " This 

 I take to be an invention applicable to various uses, such as fishing for 

 pearl, diving for coral, sponges, and the like, in far greater depths than 

 has hitherto been thought possible. Also for the fitting and plaining 

 of the foundations of moles, bridges, &c., upon rocky bottoms ; and for 

 the cleaning and scrubbing of ships' bottoms when foul, in calm weather 

 at sea." '* But," he adds, " as I have no experience of these matters, I 

 leave them to those that please to try." To several of these purposes 

 the diving-bell has, since the date of this paper (1717), been applied 

 with great advantage. 



In 1732 a communication was made to the ' Philosophical Transac- 

 tions,' No. 444, vol. xxxix., p. 377, by Martin Triewald, "Captain of 

 Mechanics, and military architect to his Swedish majesty," respecting 

 an improvement of the diving-bell. He had the sole privilege of diving 

 upon the coasts of the Baltic belonging to the king of Sweden ; and he 

 expresses his opinion, founded on much experience, that no apparatus 

 but that on the principle of the " campana urinatoria," or diving-bell, 

 could be safely used at great depths. His letter mentions a man, then 

 sixty-three years old, who had followed the business of diving with the 

 common diving-bell ever since he was twenty. Triewald's diving-bell 

 was of copper, tinned inside, smaller than that of Dr. Halley, and 

 managed by two men. A stage for the diver to stand upon was sus- 

 pended at such a depth below it, that the man's head would be but 

 little above the level of the water, where the air is cooler and fitter for 

 respiration than in the upper part of the bell ; and a spiral tube was 

 attached to the inside of the bell, with a wide aperture at the bottom, 

 and a flexible tube and mouth-piece at the top, so that, when the diver 

 was up in the bell, he might inhale cool air from the lower part, ex- 

 haling the foul air by his nostrils. Dr. Halley's air-barrels are appli- 

 cable to a bell of this construction. In lieu of windows of flat glass, 

 Triewald used convex lenses to admit light to the bell. 



In 1775 Mr. Spalding, of Edinburgh (who, according to the ' Annual 

 Register,' vol. xix., p. 202, was a grocer), having some concern in a 

 vessel which had been lost on the Fern Islands, was induced to make 

 some experiments with Dr. Halley's diving-bell, with a view to re- 

 covering property from wrecks, and was thereby led to the invention 

 of means for rendering it more safe and manageable. For these in- 

 ventions he received, in 1 776, a reward of twenty guineas from the 

 Society for the Encouragement of Arts, Manufactures, and Commerce, 

 in the first volume of whose ' Transactions ' (pp. 220-238) they are fully 

 described. Mr. Spalding"s communication contains also a very inte- 

 resting account of his experiments with Halley's diving-bell. The 

 improved diving-bell contrived by Mr. Spalding was made so light, 

 that, with the divers and the weights attached to the rim, it would not 

 sink ; the weight necessary to counteract its buoyancy being added in 

 the form of a large balance-weight, suspended from its centre by a long 

 rope, which was so mounted on pulleys that the divers could either 

 draw the balance-weight up to the mouth of the bell or allow it to fall 

 to a considerable depth below it. Thus, by letting the weight down 

 to the bottom, the divers could, as it were, anchor the bell at any 

 required level ; or prevent its further descent if they perceived a rock 

 or part of a wreck beneath it, which might otherwise overturn it. 



