DIVING BELL. 



11 



Diving Bfll. 



Its advanta- 

 ges. 



riginal 

 diving bell. 



Compres- 

 sion of the 

 air onuses 

 pain in the 

 ears, and 

 <lmii wa- 

 cr into the 

 bell. 



DIVING BELL, a. chest or tub, usually of a conical 

 shape, beneath which, when inverted, divers may de- 

 scend to very considerable depths under water ; and 

 though the bell is open at bottom, the air it con- 

 tains prevents the water filling it, because the air can- 

 not escape from the top of the vessel. At the same time, 

 through the open bottom they can gain access without 

 any obstruction to whatever they may find ; and this cir- 

 cumstance gives the diving bell a great advantage over 

 any other contrivance for the same purpose. Most of 

 the successful enterprizes in diving for shipwrecked 

 treasures, have been carried into effect by the assistance 

 of the diving bell, in preference to any other contri- 

 vance ; because in it the divers have room to move, and 

 act with perfect freedom, to employ tools for breaking 

 into ships, removing stones, &c. They can descend 

 two, three, or more in a company, if they wish to ac- 

 complish any great object at the bottom of the sea. It 

 is also a great advantage, that they can carry down 

 lights, which though not absolutely necessary, are very 

 useful in discovering the object of the diver's search. 

 Lastly, the bell will admit of diving in greater depths 

 than any other method, and of a longer continuance at 

 the bottom. 



The usual construction for a diving bell, is that of a 

 cask or tub of wood, in the form of a truncated cone, 

 the base being open, and the smaller end well closed, 

 as every part must be at its joints, and strongly bound 

 by hoops on the outside. It is poised by lead weights, 

 attached to it round the open end, till it will sink with 

 the open end downwards, when full of air, and is so 

 suspended by a rope, that it will descend in a perpen- 

 dicular direction and no other, that the open end or 

 lower edge of the bell may close upon the surface of 

 the water all round at once. Seats are fixed on the 

 inside for the divers to sit upon when they are let 

 down into the water, beneath the shelter of the bell, 

 1'rom which the air cannot escape, because it is made 

 tight in all parts except the bottom, and to get out there 

 it must first descend beneath the surface of the water, 

 in the bell, which will be considerably above the 

 lower edge; for as the bell descends, the pressure 

 of the water upon the included air compresses it into 

 a smaller space than it before occupied, and this con- 

 densation increases with the depth from the surface, 

 according to the weight of water acting upon it. At 

 thirty-three feet deep, the air will be condensed into 

 half the space, and the bell will therefore be half full of 

 water, and the air will have an elastic pressure of two 

 atmospheres. A man will not experience any great in- 

 convenience from being a short time confined in such 

 condensed air, because it is taken in by the breath, and 

 soon insinuating itselt into all the cavities of the body, 

 has no sensible effect, provided the bell is allowed to 

 descend slowly, to give time for that purpose. When 

 the bell is let down suddenly, a pressure is first felt on 

 each ear, which, by degrees, grows painful, as if a 

 quill were forcibly thrust into the hole of the ear ; but 

 as the condensed air guins admission by degrees into 

 the internal cavities of the ear, the pain ceases. When 

 the bell is drawn up again, the condensed air finds a 

 much easier passage from those cavities, without oc- 

 casioning any pain. The force thus exerted upon the 

 auditory passages might be expected to be prejudi- 

 cial to the hearing, but experience shews that this is 

 not the case. 



A real inconvenience is experienced from the di- 

 minished capacity of the bell, which becomes filled 

 with water, in proportion to the depth. Hence the 

 pace occupied by the air in the upper part of the 



bell will bear the same proportion to the lower part of Diving Bell, 

 it, which is filled with water, as thirty-three feet does w "Y~~ 1> ' 

 to the depth from the bell to the surface ; therefore, if 

 the bell is at thirty-three feet depth, the two will be 

 equal, consequently the bell will be half full of water, 

 when the air, being crowded into such a small space, 

 will soon become heated, and unfit for respiration, and 

 the bell must be drawn up to recruit it, not to mention 

 the unpleasant situation of the diver, who must be al- 

 most covered with water in the bell, and will not be 

 able to endure the cold and pressure of the water. Re- 

 specting the air, it has been estimated, that a man can 

 subsist an hour in a bell containing a ton, when at a 

 depth of thirty or thirty-five feet. 



This simple diving bell, which, from the defects above History of 

 stated, is not applicable for diving in deep water, is by the bcD - 

 no means a modern invention. Aristotle speaks of a 

 kind of kettle, used by divers, to enable them to re- 

 main for some time under water, but does not clearly 

 describe the manner in which they were used. Pro- 

 fessor Beckman informs us, that the earliest mention 

 of the use of the diving bell in Europe, is that of John 

 Taisnier, who was born in Hainault in 1 509, and had 

 a place at court under Charles V. whom he at- 

 tended on his voyage to Africa. He relates in what 

 manner he saw, at Toledo, in the presence of the em- 

 peror and several thousand spectators, two Greeks let 

 themselves down under water, in a large inverted kettle 

 with a burning light, and rise up again, without being 

 wet. It appears that this art was then new to the em- 

 peror, and the Spaniards, and that the Greeks were 

 requested to make the experiment, in order to prove 

 the possibility of it. 



In an old book on fortification, by Lorini, he describes 

 a diving machine, consisting of a square box, bound 

 round with iron, and furnished with windows ; it has 

 a stool affixed in it for the diver. The contrivance is 

 probably elder than this Italian writer, as he does not 

 "pretend to be the inventor of it. From this time the 

 diving bell was frequently employed to recover valu- 

 able wrecks, but from the defects above described, it 

 could not be used in great depths. It was not until 

 Dr Halley began his experiments, that adequate reme- 

 dies were provided. This ingenious philosopher invent- Dr Hal ' e )' !s ' 

 ed means to convey air down to the diving bell, where- 

 by not only the included air is renewed for breath- 

 ing, but the whole of the water is kept out from the 

 bell, whatever the depth may be, and air may be fur- 

 nished in any desired quantity. He describes his ap- 

 paratus in the following manner, in the Philosophical 

 Transactions : 



" The bell I made use of was of wood, containing Dimension!. 

 about sixty cubic feet in its concavity, and was of the 

 form of a truncated cone, whose diameter at top was 

 three feet, and at bottom five ; this I coated with lead, 

 so heavy that it would sink empty, and I distributed its 

 weight, about its bottom, so that it would go down in a 

 perpendicular situation, and no other ; in the top I 

 fixed a strong but clear glass, to let in the light from 

 above, and likewise a cock to let out the hot air that 

 had been breathed ; and below, about a yard under 

 the bell, I placed a stage, which hung by three ropes, 

 each of which was charged with about one hundred 

 weight, to keep it steady. This machine I suspended 

 from the mast of a ship by a spreit, which was suffi- 

 ciently secured by stays to the mast head, and was 

 directed, by braces to carry it over board, clear of the 

 ship's side, and bring it again within board. 



To supply air to this bell, when under water, I Air barrels. 

 caused a couple of barrels, of about thirty-six gallons 



