Jome Experiments made with an Air-pump. 631 
Subfiances put into the receiver. 
Weight 
when put 
Degrees of exhauft- 
ing according to 
Change in 
weight 
during the 
experiment,. 
•Ul, 
r — 
Barom. 
gage. 
Pear- 
gage- 
exp. xxviii. A piece of charcoal, 
exp. xxix. The receiver heatecU 
by holding feveral pieces of 
lighted charcoal in it, and 
then the above piece being }> 
thoroughly lighted was put 
into the receiver, and the 
pump worked^ - — ^ 
ex p. xxx. Cam phi re, — 
exp. xxxi. Sulphur made to burn”] 
on a piece of brafs, — J 
1 00 grains 
129 
650 
3°4 
247 
.1 
1 Boo 
600 
520 
320 
- 
| loft barely 
1 1 a grain* 
Obferving by thefe experiments that the fmall quan- 
tity of moifture which exhaled from the fubftances un- 
der the receiver prevented the pump from exhaufting it 
to any very conliderable degree, I began to fufpedt that 
whenever wet leather had been ufed to connect the re- 
ceiver with the plate, there mull have rifen fo great a 
quantity of vapour as to have prevented the degree of 
exhauition from being near fo great as in fome of the 
foregoing inftances. Thefe fufpicions induced me to 
make the following experiments. 
