6o PROTO-BATHYSPHERES 



than upon land. This experiment being tried, I then began 

 to think of making my engine, which was soon made, by 

 a cooper, in Stanhope Street, London, of which you have 

 the following description (Fig. 14). It is made of 

 wainscot, perfectly round, about six feet in length, about 

 two feet and a half diameter at the head and about eighteen 

 inches diameter at the foot, and contains about 30 gal- 

 lons; it is hoop'd with iron hoops without and within, to 

 guard against pressure; there are two holes for the arms; 

 and a glass about four inches diameter, and an inch and 

 a quarter thick, to look thro', which is fixed in the bot- 

 tom part, so as to be in a direct line with the eye; two 

 air-holes, upon the upper part, into one of which air is 

 conveyed by a pair of bellows, both of which are stopt 

 with plugs, immediately before going down to the bot- 

 tom. At the foot part there's a hole to let out water some- 

 times; there's a large rope, fix'd to the back or upper part, 

 by which it's let down; and there's a little line, called a 

 signal line, by which the people above are directed what 

 to do, and under is fix'd a piece of timber, as a guard for 

 the glass. I go in with my feet foreward, and when my 

 arms are got thru' the holes, then the head is put on, 

 which is fastened with scrues. It requires 500 weight to 

 sink it, and take but 1 5 pound weight from it, and it will 

 buoy up on the surface of the water. I lie straight on 

 my breast, all the time I am in the engine, which hath 

 many times been more than 6 hours, being, frequently, 

 refreshed upon the surface, by a pair of bellows. I can 



