Condensation & Rarefaction of Air. 5l9 
EXPERIMENT 4. 
Inclosed a wine glass with about a cubic inch 
of water in it, containing the bulb of a thermo- 
meter, in a receiver ; and, exhausting the air, the 
thermometer sunk half a degree suddenly, and 
then continued stationary ; upon restoring the 
_ air it suddenly rose half a degree, 
All these experiments confirmed my conjec. 
ture of a much greater degree of heat and cold 
being produced in these cases than the thermo- 
meter points out, but that its continuance is so 
short as not to effect a material change in the 
temperature of the mercury. The following 
experiments were made to ascertain what may be 
the real degree of heat and cold generated in 
those operations, 
EXPERIMENT 5, 
The samereceiver & small thermometer as above 
being used, I found the exhaustion was effect 
ed by working the pump one minue. The ther. 
mometer sunk nearly 2°in the first half minute, 
and the remainder, a few tenths of a degree, in 
the latter half minute. The operation being 
Stopped, and things remaining in the same 
State, it required some minutes of time 
before the thermometer recovered one degree 
VOL. v. cc 
