294 Church—Underground Temperatures on the Comstock Lode. 
“split” or secondary air-current was found to contain 7200 
cubic feet, and for the purpose of illustrating the steady flow 
of heat from the rock, we may reasonably assume that 18,00 
cubic feet of air enter the mine every minute, and that this 
current is divided into three splits of 6000 cubic feet each, 
which pass from the south winze 418 feet to the north winze, 
on each of the three levels, 1732, 19385, and 2040. The sec- 
ond of these is out of consideration, from the fact that there 1s 
only one thermometer on it, so that no comparison of the 
initial and final temperatures can be made. 
e following tables contain a summary of all the observa 
tions which I have been able to obtain. ‘The record is imper- 
ect on account of the destruction of some tally boards, and 
this has compelled me to omit some records that are preserved, 
because the corresponding observations in the same drift are 
wanting. ere the omission takes place, the figures are 
. 
n brackets. | 
Only the observations on the 1732 and 2040 foot levels will 
1732 foot level _ (89°39° —78-06°) 11°33° F. 
oer Fs = (92°30° — 85°35°) 695° F. 
This difference represents the heat which the air current 
has 
absorbed in passing a distance of 413 feet on these levels. In: 
my report made to Lieutenant Wheeler, and also in a paper 0? 
this subject presented to the American Institute of Mining 
ie SaaS eees 
