1879*] The Heat of the Comstock Mines, 223 
pyrite and other sulphides is not large for the neighbourhood 
of a mineral lode, but on the contrary, strikingly small, and 
not sufficient to maintain the heat of the rocks and water, 
except under circumstances of unusually rapid oxidation. 
That no metallic oxidation of any moment goes on in these 
rocks is susceptible of proof. The metallic sulphurets in 
the rock show little sign of decomposition ; and this is true 
even in layers of the propylite, that are fissured and seamy 
and drenched with water, whether hot or cold. In faCt, the 
preservation of the sulphur compounds, in presence of so 
much heat and moisture, is a noticeable facft, which the author 
has frequently remarked in all the mines. The analyses of 
such of the mine waters as he has been able to find confirm 
this statement. 
The author says the quantity of water pumped from the 
mines the past year must have been as much as 350,000 or 
400,000 tons a month. If its temperature is assumed to be 
only 135 5 F., and the average temperature of the air for the 
year 50°F., we have in the year, say, 350,000 x 12 = 4,200,000 
tons of water raised 85 degrees in temperature ; or, as the 
usual expression is, 4,200,000x85 = 357,000,000 ton-heat 
units have been absorbed by the water. If the heating- 
power of anthracite coal is estimated at 7500 heat units to 
the ton, the heat in this water is as much as would be ob- 
tained from the combustion of 47,700 tons of coal. A cord 
of pine wood weighing 2700 pounds will probably give about 
4300 heat units in practice, so that 84,000 cords would be 
necessary to keep up the heat withdrawn from the rocks in 
the mine waters alone. 
If 10 tons of air pass through the mines collectively each 
minute, or 14,400 tons daily, and the air when discharged 
from the mines has an average temperature of 92° F., the 
total quantity of air for the year will be 5,256,000 tons, and 
the average rise in temperature 42 degrees. The specific 
heat of air being 0*267, we have — 
5,256,000 x 0*267 x 42 = 58,940,784 ton-heat units 
for the amount of heat absorbed by the air. This corre- 
sponds to an expenditure of 7859 tons of anthracite coal, or 
13,707 cords of wood. The total quantity of heat carried 
out of the mines yearly by the water and air is therefore 
416,000,000 ton-heat units, to produce which, in ordinary 
industrial operations, would require 55,560 tons of anthra- 
cite, or 97,700 cords of wood. 
The number of men employed under ground in the mines 
of the upper Comstock is less than three thousand, and the 
