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.^Notice in regard to the Temperature 
of Mines, 
By Mathew Miller, Esq. 51st Light Infantry, 
M. W. S. 
{Read Sth February 1823.) 
The late experiments on the temperature of mines made 
in Cornwall, and in other countries, having given rise to 
various speculations in regard to the distribution of heat 
in the crust of the earth, all of which appear to me to be 
unsatisfactory, I now beg leave to offer for consideration of 
the Society, an explanation, which does not seem liable to 
the objections that have been opposed to the others. 
In every mine, with the exception of a few, which are 
level-free, the ventilation is carried on by causing the air at 
the surface to descend, and traverse the works, and then 
ascend. Now, it is evident, that if a portion of air from 
the surface be carried down to the bottom of the mine, it 
will be condensed in proportion to the depth of the mine, 
and, in consequence of this condensation, will become 
heated, and the degree of heat will of course be in propor- 
tion to the depth of the mine. The air thus heated tra- 
