20 5 
On the changes of volume produced in gases, &c. 
tion to the Society, induced me to undertake the following 
experiments. 
Dry atmospherical air was included in a tube by mercury, 
and its temperature raised from 32 0 Fahrenheit to 212 0 , and 
its expansion accurately marked. The same volumes of air, 
but of double and of more than triple the density under a 
pressure of 30 and 65 inches of mercury, were treated in the 
same manner, and in the same tubes ; and when the neces- 
sary corrections were made for the difference of pressure of 
the removed column of mercury, it was found that the ex- 
pansions were exactly the same. 
An apparatus was constructed, in which the expansions of 
rare air confined by columns of mercury were examined and 
compared with the expansions of equal volumes of air under 
common pressure ; when it appeared, that for an equal num- 
ber of degrees of Fahrenheit's scale, and between 32 ° and 
212 0 they were precisely equal, whether the air was ■£., or £ 
of its natural density. < 
Similar experiments were made, but they were necessarily 
less precise, with air condensed six and expanded fifteen 
times, with similar results. 
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