Chap. 3.] Pump. 453 



only to the height of thirty-two feet. M. Brifibft has 

 carefully examined into the fad, and his explanation is 

 curious and interefting. 



An ignorant tinman, at Seville, had made a fucking 

 pump fixty feet long, becaufe he had occafion to ele- 

 vate the water to that height. When the pump was 

 fixed in its place, and put in action, he was unable to 

 make the water rife into the body of the pump. En- 

 raged at this difappointment, he gave it a blow with 

 Jiis hammer, which produced a fmall aperture in the 

 afpiration pipe at about ten feet above the furface of 

 the water in the bafon. Immediately a fmall portion 

 of water arrived at the body of the pump. After this. 

 procefs it was reported, that a fucking pump had 

 been conftructed, which elevated water to the height 

 of fixty feet; but the reader will be enabled to judge 

 of the truth of this aflertion from the following obfer- 

 vations : 



Let us fuppofe that the afpiration pipe, P F (Plate 

 VIII. Fig. i.) had from a, the furface of the water 

 of the bafon, to F, a diftance of fixty feet, and that 

 after a certain number of ftrokes of the pifton, the 

 water rifes to <r, thirty-two feet high ; if then a fmall 

 hole is made at b, ten feet above the furface of the 

 water, the air which enters at this hole, and preffes 

 in all directions, will caufe the column of water of ten 

 feet, which is below , to fall into the bafon, and the 

 prefiure of the air upwards at b has only a column of 

 water of twenty-two feet to fupport. 



But that preffure is capable not only of raifing that 

 column to the height of fixty feet, but even to the 

 height of eight thoufand feetj for air, near the furface 

 of the earth, is eight hundred times lefs denfe than 

 water, and fuppofing (which is not the cafe) it was 

 #0 1 diminiihed in elevating, then the ten feet of water, 

 Q g 3 e u t 



