260 PHILOSOPHICAL TRANSACTIONS. [aNNO 17 16. 



filled with water, as 33 feet to the depth of the surface of the water in the bell 

 below the common surface of it. And this condensed air, being taken in with 

 the breath, soon insinuates itself into all the cavities of the body, and has no 

 sensible effect, if the bell be permitted to descend so slowly as to allow time for 

 that purpose. The only inconvenience that attends it, is found in the ears, 

 within which there are cavities opening only outwards, and that by pores so 

 small as not to give admission even to the air itself, unless they be dilated and 

 distended by a considerable force. Hence on the first descent of the bell, a 

 pressure begins to be felt on each ear, which by degrees grows painful, like as 

 if a quill were forcibly thrust into the hole of the ear ; till at length, the force 

 overcoming the obstacle, that which constringes these pores yields to the 

 pressure, and letting some condensed air slip in, present ease ensues. But the 

 bell descending still lower, the pain is renewed, and again eased after the same 

 manner. On the contrary, when the engine is drawn up again, the condensed 

 air finds a much easier passage out of those cavities, and even without pain. 

 This force on the auditory passages might possibly be suspected to be prejudicial 

 to the organs of hearing, but that experience shows the contrary. But, what 

 is more inconvenient in this engine, the water entering into it, so as to contract 

 the bulk of air, according to the aforesaid rule, into so small a space, as that it 

 soon heats and becomes unfit for respiration, for which reason it must be often 

 drawn up to recruit it : and besides, the diver being almost covered with the 

 water thus entering into his receptacle, will not be long able to endure the cold 

 of it. 



Being engaged in an aflfair that required the skill of continuing under water, 

 I found it necessary to obviate these difficulties, which attend the use of the 

 common diving-bell, by inventing some means to convey air down to it, while 

 below; by which not only the included air would be refreshed and recruited, 

 but also the water wholly driven out, in whatever depth it was. This I effected 

 by a contrivance so easy, that it may be wondered it should not have been 

 thought of sooner, and capable of furnishing air at the bottom of the sea in 

 any quantity desired. The description of my apparatus is as follows : 



The bell I used was of wood, containing about 6o cubic feet in its concavity, 

 and was of the form of a truncated cone, the top diameter 3 feet, and the bot- 

 tom 5. This I coated with lead so heavy that it would sink empty, and I dis- 

 tributed the weight so about its bottom, that it would go down only in a per- 

 pendicular situation. In the top I fixed a strong clear glass, as a window 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 3 ropes, each of which was charged with about a hundred weight, to keep it 



