290 Church—Underground Temperatures on the Comstock Lode. 
The rock in the lower levels (1900-2000 feet) of the Com- 
stock mines appears to have a pretty uniform temperature of 
130° F. This was the reading obtained for me on several occa- 
sions by Mr. Comstock, foreman of the Ophir mine, and about 
the same temperature was found by Mr. Perrin, foreman of the 
Chollar Potosi, by Mr. Cosgrove, foreman of the Yellow Jacket 
(1894° F. and 136° F., 2200 foot level), and by myself in the 
Crown Point and other mines. ese readings were obtain 
by placing a thermometer in a drill-hole immediately after the 
hole was finished, and leaving it there for periods varying from 
ten minutes to half an hour. 
Mining on the Comstock proceeds with extraordinary ae 
ve, 
eep. 
The surface of the rock exposed to the air of the drift was 
found on one occasion to be about 123° F., the experiment 
being made near the “header” or end of the drift. The alr 
itself was found to show considerable uniformity when its tem- 
perature was taken under circumstances that were at all similar. 
n freshly opened ground it varied from 108° to 116° F., and 
higher temperatures are reported at various points, reaching 1 
fact as high as 123° F. in the 1900 level of the Gould & Curry. 
The temperature of the air is subject to more fluctuations 
than that of the rock, for the simple reason that it is artificially 
supplied to the mine, and varies according to the istance 
which it is carried, the quantity, velocity in the pipe, 1ts rea 
temperature, and moisture in the drift. The most importap 
