624 Mr. nairne’s Account of 
“ the common gages fhew how much the prefllire of 
“ the included fluid is diminiflied, and that equally, 
“ whether it conlift of air or of vapour.” 
Mr. cavendish having explained fo fatisfa£torily the 
caufe of the difagreement between the two gages, I con- 
fidered, that, if I were to avoid moifture as much as pofft- 
ble, the two gages fliould nearly agree: this induced 
me to make the following experiment. 
EXPERIMENT III. 
The plate of the pump being made as clean and as 
dry as poflible, there was then put on it the before- 
mentioned fliort barometer-gage, alfo the pear-gage 
with a ciftern entirely of glafs which held the quick- 
lilver; they were then covered with a receiver, round 
the outfide of which was laid a cement which per- 
fe£fly excluded the outward air; every part, before it 
was put under the receiver, as well as the receiver itfelf, 
being made as clean and as free from moifture as poili- 
ble^. The pump was then worked for ten minutes, 
(a) It may be proper here to take notice, that the pump in every experiment 
hereafter mentioned was worked ten minutes, and the fame receiver continued 
cemented to the pump-plate, except where it is otherwife mentioned. The top 
part of this receiver was made to open, in order to put in different things. 
3 and 
