86 \ | Ban-Marum’s Gaxometer 
will be; conveyed from that veflel where it has the greateft 
height into the other, until the water in both be of the fame 
height. For example, when the water in the cylinder H 
ftands at K, and in the glafs A at L (in which cafe we muft 
fuppofe the cock D open that the air may efcape), the water 
will continue to flow from H into A till it ftands at the fame 
horizontal line. 
‘The higher the water K is raifed in H the greater is the 
weight of the column, and the quicker the efcape of the air. 
By thefe means M, Vén Marum obtains what Meffieurs La- 
voifier and Meufnier call preffure in the ¢azometer, merely 
by the higher level of the furface K over L. That the height 
of the water in H may be obferved, a glafs tube M M about 
1}inch in diameter, and conneéted with it, is placed be- 
tween H and A, in which the water will always have the 
fame altitude as in H. An ivory feale, divided into inches 
and lines; faftened to a cork ball, floats upon this water, and 
ferves to thew the difference of the altitudes of the water at 
L and K. 
The cock N, fitted to the top of the open cylinder O, ferves, 
together with the cock P, to preferve the preffure perfectly 
uniform. ‘Suppofe, for example, that a conftant preffure of 
water of two inches high was required, as much water muft 
be fuffered to flow continually into Has ‘is equal in bulk to 
the quantity of water that this preflure of two inches forces 
from EL into A. For this purpofe, fill the cylinder O with 
water to the height of {eur inches, and turn the cock N un- 
til the preffure of the four inches of water, which is main- 
tamed, by the cock P, forces through N into H a ‘quantity 
of water exactly equal to the quantity that the preffure of 
two inches forces from H into A, The index Q of the cock 
N, and the feale RS, ferve to give to the cock N the exa& 
opening required; this having been determined beforehand, 
and the feale divided accordingly, 
The‘cock N begins to open when the index R is turned 
towards S ; and, for this reafon, the gradation of the feale 
ff begins 
