636 Mr. nairne’s Account of 
not being able to exhauft beyond the low degrees of 7 o 
or 80. Had he been aware of the bad effects of fetting 
the receiver upon leather foaked in water and fpirit of 
wine ; and had he made ufe of the precaution to free all 
parts of his pump as much as poffible from moifture, I 
make not the leaft doubt but the air-pump, which he 
executed himfelf, would have exhaufted to as great a 
degree, as that pump has been feen to have done with 
which the chief of thefe experiments were made. 
Having read the principal part of this paper to Mr. 
smeaton, and fliewn him fome of the experiments; 
one in particular, where the pear-gage, as he obferved 
himfelf, was filled to no left than 100,000th part of the 
whole content; he remarked from memory, that he had 
in feveral trials exceeded 1000 times, and once, as he 
remembered, near or about 10,000 times; but as he 
never could account how this happened, which appeared 
to him perfectly accidental, and therefore could not de- 
pend upon doing it at pleafure, he contented himfelf with 
putting down 1000 times, as being wffiat (under the cir- 
cumftances mentioned in his papers) he had a tolerable 
certainty of. 
I mull here again obferve, that if we only wilh 
to knoW the quantity of permanent air remaining 
in the receiver after it is as much exhaufted as poffi- 
ble, 
