DIVING BELL. 



13 



With air 

 pipes 

 from the 

 great bell. 



Diving Bell, water in the cap was above the level of that in the bell, 

 ^^Y"^ by means of a flexible pipe which he could carry coil- 

 ed on his arm. 



In pursuance of this idea, he procured pipes to be 

 made, which answered all that was expected from them. 

 They were secured against the pressure of the water 

 by a spiral brass wire, which kept them open from end 

 to end, the diameter of the cavity being about the sixth 

 part of an inch. These wires being coated with thin 

 glove leather, and neatly sewed, were dipped into a 

 mixture of hot oil and bees wax, which, filling up the 

 pores of the leather, made it impenetrable to water ; 

 several thicknesses of sheep's entrails were then drawn 

 over them, which, when dry, were covered with paint, 

 and then the whole defended with another coat of 

 leather to keep them from fretting. Several of the 

 pipes were as much as forty feet long, the size of a half 

 inch rope ; one end of a pipe being fixed in the bell 

 at some height above the water, the other end was fas- 

 tened to a cock which opened into the cap. The use 

 of the cock was to stop the return of the air whenever 

 there was occasion to stoop down or go below the sur- 

 face of the air in the bell, which occurred as often as 

 there was occasion to go out or return into the machine. 

 The diver, therefore, when he has descended to the 

 bottom in the great bell, puts on his cap with the pipe 

 hanging on his arm like a coil of rope. As soon as he 

 leaves the bell, he opens the cock in the pipe, and 

 walks on the bottom of the sea, giving out the coils 

 of his pipe as it is required; and this serves as a clue 

 to direct him back again to the great bell, from whence 

 he derives his supply of air by means of the pipe. 



The weight of a man being very little more than that 

 of his bulk in water, he could not act with any strength, 

 nor stand with any firmness, especially if there is any 

 current, without a considerable addition of weight; the 

 leaden caps were therefore made to weigh about half a 

 hundred weight, to which was added a girdle for the 

 waist, formed of large weights of lead nearly of as great 

 weight in the whole ; also two clogs of lead for trie feet 

 of about 1 2 pound each. With this accession of weight, 

 Dr Halley, found a man could stand well in an or- 

 dinary stream, and even go against it. It is necessary 

 for the diver to l>e provided against the cold of the wa- 

 ter, which, though it could not be removed so that a 

 man could endure it long, yet it was much eased, by 

 wearing a waistcoat and drawers made close to the bo- 

 dy, of that thick woollen stuff of which blankets are 

 made ; this becoming full of water, would be a little 

 warmed by the heat of the body, and keep off the chill 

 of new cold water coining on. 



When the water is not turbid, things are seen suffi- 

 ciently distinct at the bottom of the sea ; but a small 

 degree of thickness makes perfect night in a moderate 

 depth of water. To obtain an open view from the 

 leaden caps, which, from their use, the Doctor called 

 caps of maintenance, he at first used a plain glass be- 

 fore the tight, but soon found that the vapour of the 

 breath made such a dew on the surface of the glass, 

 that it lost iu transparency ; to remedy this, he found 

 it necessary to prolong that side of the cap which was 

 before the eyes, and thereby enlarge the prospect of 

 what was beneath. 



Mr Martin Triewald, who was military architect to 

 the king of Sweden, proposed another form of the di- 

 Ting-bell adapted for a single diver, which, being on a 

 PI.ATB small scale, may be made at a less expence than Dr Hal- 

 CCXXXI ky' 8 ; ar) d drawn up with more convenience. It is re- 

 Fig. 10. presented in Fig. 8. Plate CCXXXI. The bell AB is 



Trictaid's 

 bell. 



made of thin copper plate, tinned on the inside, and Diving Bell, 

 stregthened without by bands of iron hoop a a en- S """Y~""'' 

 compassing it in different directions. It is suspended PIATE 

 by a rope C, from the ring A at the top and caused CCXXXI. 

 to sink perpendicularly by weights DD suspended Fi S- 10< 

 from the bottom hoop, as well as by a large iron ring 

 or plate E, which is suspended at such a distance from 

 the bottom of the bell by chains, that when the diver 

 stands upright with his feet upon this plate, his head is 

 above the water in the bell. This situation is better than 

 if his head was in the top part A of the bell, the air be- 

 ing cooler and more pure near the surface of the water 

 than higher up, because the air which has been breath- 

 ed is heated, and rises up to the top ; but when it is ne- 

 cessary for the diver to rise up into the top of the bell, 

 the inventor has provided him the means of draw- 

 ing up the cool air from the bottom near the water. 

 This is a spiral copper tube, shewn by the dotted 

 lines b c. It is placed round the inside of the bell, the 

 lower end opening in the bottom of the bell, and the 

 upper end provided with a flexible leather tube end- 

 ing in an ivory mouth-piece d, for the diver to hold in 

 his mouth and inspire the air from below ; whilst at 

 every expiration he throws out the air through his nos- 

 trils into the upper part of the bell. This bell may be 

 supplied with fresh air from barrels in the same man- 

 ner as Dr Halley's ; and is therefore provided with a 

 cock in the top to allow the impure air to escape when a 

 fresh supply is obtained. It is illuminated by four strong 

 lenses in the top, at GGG, each provided with copper 

 shutters, to defend them from accidents when on shore. 

 Several important improvements were made in the 

 diving bell in 1776, by Mr Spalding of Edinburgh, to ^. Ir S P" U 

 whom the Society of Arts presented a reward for the in- " n "' 

 vention. This gentleman had in thetwo preceding years, 

 acquired considerable experience in the management of 

 a bell on Dr Halley's plan, which he had constructed, 

 in the hopes of recovering some of a considerable pro- 

 perty which was lost in a ship that was wrecked on the 

 Scares, or Fern Islands, in 177*, in the night, when all 

 the crew perished. Some of the light goods were thrown 

 on shore; and it was proposed to recover the rest by di- 

 ving, the remainder of the owners giving up the ma- 

 nagement of the whole to Mr Spalding. His first ex- 

 periments were made in depths of 5, 6, and 8 fathoms His descent , 

 in Leith roads; and having in these made his apparatus in Dr Hal- 

 tolerably perfect, he sailed for Dunbar, thirty miles dis- le y' s bel1 

 tance, in an open long boat, sloop rigged, and of about 

 six or eight tons burthen. By a mistaken account, he 

 had been iiformed the bottom of the Fox ship of war 

 lay there ; but upon his arrival,, the oldest seaman in the 

 place could give him no intelligence, as that vessel pe- 

 rished in the night, with all on board, somewhere in 

 Dunbar bay, and by storms, during so long a period as 

 thirty years, was thought to be sanded up. In order to 

 gratify the curiosity of some friends there, he still de- 

 termined to descend where it might be thought proba- 

 ble her bottom lay ; but in seven and eight fathoms wa- 

 ter found nothing but a hard sandy bottom, from 

 whence he was led to conjecture, that the proprietors 

 of the valuable effects which were on board that ves- 

 sel, might have found their account in sweeping 

 for her. Being informed that a vessel, which was 

 thrown up by accident in the river .'fay, near Dundee, 

 with a large quantity of iron, lay within two fathoms 

 of the surface at low water, he determined to make trial 

 there, and accordingly sailed across the frith to that gt 

 place, about fifteen leagues distant from Dunbar. Here 

 be went down three different times, changing the 



