[ 2?8 ] 
iTienfions, for the fervice of the kitchen offices. Nowit is 
to be obferved, that the kitchen offices are lituated at leaft 
eighteen or twenty feet below the fnrface of the refer- 
voir A, and that the cock F is about fixteen feet below 
it. G reprefents a valve-box, g the valve, H an air- 
velTel, 00 the ends of the main-pipe inferted into H, and 
bending downwards, to prevent the air from being driven 
out when the w'ater is forced into it, w the furface of 
the water. Now it is w'ell known, that water difcharged 
from an aperture, under a preffure of hxteen feet per- 
pendicular height, moves at the rate of thirty-two feet 
in a fecond of time; therefore fuch will be the velocity 
of the water from the cock F. And although the aper- 
ture of the cock F is not equal to the diameter of the 
pipe D, yet the velocity of the water contained in it will 
be very conhderable : confequently, when a column of 
water, two hundred yards in length, is thus put into 
motion, and fuddenly flopped by the cock F, its mo- 
mentous force will open the valve g, and condenfe the 
air in H, as often as water is drawn from F. In what 
degree the air is thus condenfed, is needlefs to fay in the 
infiance before us ; therefore I fliall only obferve, that 
it was fufficiently condenfed to force out the v/ater into 
the refervoir K, and even to burft the veffel H, in a few 
months after it was firfl conftrudled, though apparently 
very firm, being made of fheet lead, about nine or ten 
pounds weight to a fquare foot. From whence it feems 
xeafonable to infer, that the momentous force is much 
* fuperior 
