Mr. nairne’s Account , See. 615 
tr about half a pound of quickfilver : it is open at one 
* ( end, and at the other is a tube, hermetically clofed 
“ at the top. By the help of a nice pair of fcales I found 
ic what proportion of weight a column of quickfilver, of 
« a certain length, contained in the tube, bore to that 
u which filled the whole veflel : by thefe means I was 
u enabled to mark divifions upon the tube anfwering to 
u a 1 oooth part of the whole capacity; which being 
** about one-tenth of an inch each, may, by eftimation, 
“ be eafily fub-divided into fmaller parts. This gage, 
“ during the exhaufting of the receiver, is fufpended 
“ therein by a flip wire. When the pump is worked as 
“ much as fhall be thought neceflary, the gage is pufhed 
** down till the open end is immerged in a ciftern of 
“ quickfilver placed underneath ; the air being then let 
“ in, the quickfilver will be driven into the gage till the 
M air remaining in it becomes of the fame denfity with 
“ the external, and as the air always takes the higheft 
** place, the tube being uppermoft, the expanfion will be 
“ determined by the number of divifions occupied, by 
u the air at the top; 
“ The degree to which I have been able to ratify the 
a air in an experiment, has generally been about 1000 
**■ times, when the pump- is put clean together; but the 
3, s< moiftu r e. 
