fame Experiments made with an Air-pump. 6 37 
ble, it feems, that it is by Mr. smeaton’s gage only 
that we can know it. Again, when by the afliftance of 
his gage and the barometer-gage together, we have dif- 
eovered that there is a vapour which arifes and occupies 
the place of the permanent air which is exhaufted, it 
feems that it is by the means of his gage only that we 
can difeover what part of the remaining contents of the 
receiver conlifts of this vapour, and what part of perma- 
nent air.. 
An account of fome further experiments made with the- 
fame air-pump on Mr. sMEATON’r principle, the refults- 
of which were different from the former. ~ 
AFTER I had made the foregoing experiments, and 
thought to have done with the fubjedt (for feme time at 
leaft) in reviewing them for the laft time, I perceived one 
or two, the extraordinary refults of which (though not 
unnoticed by me before) I now thought I had, not paid 
fufficient attention to. Experiment the 19th (in which 
I found that when vitriolic acid was put into the receiver, 
and the pump worked for the ufual time, the pear- 
gage indicated a much lefs degree of exhauilion than the 
barometer-- 
