PNEUMATIC'S. lfjl 



effects; and that he might have continued there as 

 long as he pleased. 



By the glass above, so much light was transmitted 

 when the sun shone, and the sea was clear and 

 even, that he could see perfectly well to read and 

 write, and to take up any thing that was under the 

 bell; and by the return of the air-barrels, he could 

 send up orders, written with an iron pen, on small 

 pieces of lead, when he wished to be moved from 

 place to place. But in misty weather, or when the 

 sea was rough, it was nearly dark in the bell, and 

 he was then obliged to burn a candle, which con- 

 sumed about as much air as one person. 



The only inconvenience which the divers felt 

 was, that upon their going down they felt a pain in 

 their ears, as if the end of a quill was thrust into 

 them, which was owing to the condensed air 

 pressing upon the tympanum. This, however, in 

 a short time ceased. 



Doctor Halley also contrived a method of send- 

 ing a man out of the bell, to some distance, by 

 means of a small bell on his head, with a glass in 

 front, and a pipe communicating with the great 

 bell, to supply him with air. 



Mr. Triewald invented a diving-bell of a different 

 form, which was much smaller and less expensive 

 than Dr. Halley's; it only covered half the body 

 of the diver, who stood upon a ring hanging from 

 the bell by chains. There was also a spiral pipe 

 within the bell, by which he could always breathe 

 the air immediately at the surface of the water in 

 the bell, which was cooler and fresher than that at 

 the upper part of the machine. 



Mr. Smeaton's diving-bell was a square chest of 

 cast-iron, 4-§- feet in height, 4* feet in length, and 

 three feet wide, and afforded room for two men to 

 vol. j. M 



