■T?2 Dcfaiption of a Second 



it poffible," fays he, " to proceed to the greateft depths 

 with the beforc-defcribed machine, difficulties may ftill arife 

 on account of the great length of the pipe ; for it may be 

 aflced, Can the diver breathe long when the column of air 

 is of fueh a length ? I have found that it is difficult to 

 breathe long through a pipe of a hundred feet, and half an 

 inch in diameter; that the brcaft foon becomes fatigued; 

 and that it is much eafier to breathe through a pipe of half 

 that length. Though a greater diameter may in part ob- 

 viate this difficulty, fo that the diver can breathe with more 

 cafe, yet another queftion arifes : At the depth of a hundred 

 feet and more, is it pofiible for the diver to manage fuch a 

 long tube conveniently, as it muft meet with refiftance ac- 

 cording to particular circumftances, and as bv its length it 

 muft acquire confiderable weight ? How would he manage 

 when he wifhcd to rife again to the furface ? and at fuch a 

 depth could he make a ftgnal for that pu-rpofe, and with fuf- 

 ftcient quicknefs ? On account of thefe queftions I turned 

 my thoughts to another machine, to be ufed in necefiary 

 cafes with the former, and I hope the one I mean to propofc 

 will be found worthy of fome notice. 



"Theflgure (Plate III.) reprefents the machine, which con- 

 Jifts of a hollow cylinder, terminating in two hollow trun- 

 cated cones. It is conftrucled in the fame manner as calks, 

 and made exceedingly ftrong. In order that the wood may 

 be rendered water-tight, it is daubed over on the outfidc 

 with any proper varnifh or cement. 



" By means of the interior conftruclion of this machine a 

 man can defcend to a great depth in the water, and live 

 and move freely without a pipe to fupply him with at- 

 mofpheric air, becaufe, being placed on a ftage without the 

 machine, and furniilied with a harnefs and pipe like that 

 before defcribed, he can obtain air from the fpace within it, 

 which contains 58 cubic feet. He may, therefore, remain 

 under water two hours ; defcend from the ftage at pleafure, 

 |jaove about with freedom, and, bv means of the machinery 



within* 



