390 tlNDEEGEOUND TEMPEEATtlEE AT DOtCOATH. 



Taking- tlie temperature of the great open spaces at 358 faths. 

 from surface as tlie normal temperature of the mine at that depth, 

 and 52° F as the mean temperature of the surface, it appears 

 that the temperature increases downwards at the rate of 1 ° F for 

 each 93 feet, which is, I believe, a considerably lower rate of 

 increase than has been hitherto observed. 



