522 PHILOSOPHICAL TRANSACTIONS. [aNNO 1721. 



receive a constant stream of air from the magazine in the great bell, so long 

 as the surface of the water in the caps was above the level of that in the bell. 



Following this idea, I procured pipes to be made, which answered all that 

 was hoped from them. They were secured against the pressure of the water, 

 by a spiral brass wire, which kept them open from end to end, the diameter 

 of the cavity being about -^ part of an inch. These wires we coated with 

 thin glove leather, curiously sewed on, and then the leather was dipped into a 

 mixture of oil and bee's-wax hot, which, filling up the pores of the leather, 

 made it impenetrable to water. We then drew several folds of sheep's guts 

 over them, which when dry, we painted with a good coat of paint, and then 

 secured the whole with another coat of leather, to keep them from fretting. 

 The pipes were about 40 feet long, the size of a half-inch rope; the one end 

 being fixed in the bell, at some height above the water, and the other end 

 fastened to a cock, which opened into the cap. The use of the cock being to 

 stop the return of the air, whenever there was occasion to stoop down, or go 

 below the surface of the air in the bell, which was necessary as often as there 

 was occasion to go out or return into the bell. 



The diver therefore putting on his cap, and coiling his pipe on his arm, like 

 a rope, as soon as he is discharged from the bell, opens his cock, and walks 

 on the bottom of the sea, vearing out the coils of his pipe, which serve as a 

 clue to direct him back again; and this I have seen practised without any ill 

 incident attending it. 



But there are two things to be remarked in this affair: first, that the weight 

 of a man being very little more than that of his bulk in water, he cannot act 

 with any strength, nor stand with any firmness, especially where any thing of 

 a stream runs, without a considerable addition of weight; and therefore the 

 leaden caps were made to weigh about half a hundred weight, to which I added 

 a girdle of large weights of leads, of about the same weight in the whole, this 

 being to be worn about the waist; and two clogs of lead for the feet, of about 

 12 lb. each. With this accession of weight I found a man could stand well in 

 an ordinary stream, and even go against it. The other thing necessary to be 

 provided against, was the cold of the water, which though it could not be 

 wholly taken off, so that a man could endure it long, yet it was much eased by 

 habits of waistcoat and drawers, made close to the body, of thick blanket 

 stuff: this being full of water would be a little warmed by the heat of the body, 

 and keep off the chill of new cold water coming on it. 



As to seeing under water, as long as the water is not turbid, things are seen 

 sufficiently distinct; but a small degree of thickness makes perfect night, at 

 no great depth of water. In my leaden caps, which from their use I called 



