i879-J 
Heat of the Comstock Mines. 
797 
still in adtive decomposition, which has been found to exist 
for a depth of about 1500 feet or more, and doubtless extends 
thousands of feet farther ; and, finally, a mass of cold rock 
at a great depth, which has not yet begun to decompose. 
He refers the high temperature not to the internal heat of 
the earth, nor to the residual heat of the rocks, which were 
once melted, but to chemical adtion now maintained in the 
erupted rocks. This adtion is not a combustion, but the 
chemical alteration of the felspathic minerals of the propy- 
lite and other rocks, the peculiar bands of hot and cold 
rocks which Prof. Church describes, being layers of rock in 
which decomposition has been delayed and hastened. 
Prof. G. F. Barker, who has also visited the mines, con- 
cludes,* on the other hand, that the heat is a hot-water heat, 
and that the waters are heated mechanically by those continu- 
ous movements of the country so plainly shown both in the 
mines and at the surface. But Prof. Church replies that al- 
though the Comstock discharges four and a half million tons 
of water yearly, not 1000 feet out of the 12 miles of linear 
excavation made every year are in ordinarily wet ground. 
The objedl of this present article is not, however, to dis- 
cuss the cause of the heat of the Comstock Mines, but to 
draw attention to the large percentage of accidents resulting 
from this intense heat. At a recent meeting of the American 
Institute of Mining Engineers, Prof. Church reviewed, at 
considerable length, these accidents and their relation to 
deep mining. From the report in the “ Scientific American ” 
we learn that during the twenty-two months preceding May, 
1879, there were 101 accidents, killing 53 persons and 
wounding 70 others. These accidents are classified as 
follows : — (1) Falls of rock, timber, &c. ; (2) Tramming ; 
(3) Effects of heat ; (4) Falls of men ; (5) Explosions ; 
(6) Hoisting apparatus ; (7) Overwinding; (8) Miscellaneous. 
In several instances miners have been fatally scalded by 
falling into the hot mine waters, which exhibit temperatures 
rising to 158° F. The most remarkable casualties, however, 
are due to the killing effedt of labour in the hot and 
steaming atmosphere. The proportion of fatal casualties 
is larger in this class than in any other, being 73 per cent ; 
and from the peculiar mental effedts of the heat it is highly 
probable that it may be the real cause of many mishaps, 
which under other circumstances would be ascribed to cul- 
pable blundering. 
On the 1900 level of the Gould and Curry mine a drift 
* See Letter by G. F. Lesley in Nature, vol. xx., p. 168. 
