515 
Experiments and Observations on the 
HEAT and COLD produced by the 
MECHANICAL CONDENSATION 
and RAREFACTION of AIR. 
BY JOHN DALTON, 
READ JUNE 27, 1800, 
I; a thermometer be inclosed in a receiver and 
the air suddenly condensed, the thermometer 
rises a few degrees above the temperature of the 
atmosphere ; and if the air be exhausted from a 
receiver inclosing a thermometer, the mercury 
sinks a few degrees immediately 3; but in both 
cases after some time it resumes its former stax 
tion. These facts are well known to philoso. 
phers of the present age, but they do not all 
agree in the explanation of them. Thinking the 
subject worthy of elucidation, I was induced to 
institute a series of experiments for the purpose; _ 
which I apprehend have led to a clear demon= 
Stration of the cause of the phenomena, and 
moreover make the facts themselves appear in a 
somewhat different point of view from what they 
re seen in at the first moment, 
