fotm Experiments made with an Air-pump. 621 
diminution of the preflure on the furface of the quick- 
filver in the tube of the long gage, and alfo on the fur- 
face of the quickiilver in the ciftern of the ihort gage. 
But of thefe two gages the long barometer-gage was 
chiefly ufed in the following experiments, as being fixed 
to the pump: however, having now made thefe two 
gages with as much accuracy as I was matter of, and 
finding that they agreed pretty nearly, I proceeded to 
repeat my firft experiment. 
EXPERIMENT II. 
I put the fhort barometer-gage, and the pear-gage 
with the glafs cup having a wooden foot,, both toge- 
ther under the receiver, which receiver was placed on a 
leather foaked in oil and tallow on the plate of the 
pump ; the pump was then worked for ten minutes, and 
the quickiilver was brought down in the ihort barome- 
ter-gage to about one-tenth of an inch of the furface of 
the quickiilver in the ciftern, and rofe in the long baro- 
meter-gage to within one-tenth of an inch of the height 
of the quickiilver in my ftandard barometer, which was 
at that time at thirty inches; by which it appeared, that 
the 
