SUBTERRANEAN GASES. 
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in winzes, from which it can be bailed or sucked out when the barometer is high, 
but when the barometer is low the gas enters more rapidly than it can be removed. 
The presence of a moderate amount of the gas in the mine atmosphere is said to 
produce irregular heart action, sweating, and weakness. If these warning symptoms 
are not heeded, asphyxia may suddenly follow. The mine was closed in March, 
1904, partly on account of the difficulty of working in the lowest levels. 
Last Dollar mine .—This mine was not troubled by gas until level 10 was 
developed. On this level, at the breasts of certain long crosscuts, a considerable 
amount accumulates at times. The gas does not interfere with the ordinary 
working of the mine. It is stated that it sometimes accumulates in the back of 
the drifts instead of on the floor; if correct, this would indicate that it is largely 
composed of nitrogen. Miners have worked in the gas for one or two days by 
electric lights when the candles would not burn, but were unable to continue longer, 
as great lassitude and pains in the back developed. 
Modoc mine. —The upper workings do not contain gas, but a 400-foot winze 
in the lower part of the workings always contains some gas and is sometimes 
entirely filled. 
Blue Bird mine. —Gas enters the mine in all levels below 4 on certain days. 
At these times the lower part of the mine is frequently inaccessible. 
Wild Horse mine. —The depth of the Wild Horse mine is 1,250 feet, the elevation 
of the collar being 10,653 feet. Complete oxidation extended down to a depth 
of 1,150 feet. There was no gas until the 1,250-foot level was opened, when it 
issued in large volumes from the porous pyritic granite-breccia which constitutes 
the country rock. The gas interfered greatly with the work and is said to have 
sometimes filled the mine almost to the collar of the shaft for several days in 
succession, especially at periods of low barometer. 
Logan and Orpha May mines. —A few records from these mines, which were 
closed in 1904, were secured from Mr. Fred Johnson, formerly in charge of the 
properties. lie states that gas was very troublesome in a crosscut east on level 
13 in the Orpha May. It also issued in large amounts from a certain place in a 
crosscut on level 12 of the Logan mine, about 500 feet northwest of the shaft. 
Ventilation had no effect, and the place was ordinarily inaccessible, so that the 
drift was temporarily barred. It is stated that the gas had the appearance of a 
“bluish haze” and that it was unusually concentrated and poisonous. Two men 
were suffocated at this place trying to make their way through it. 
Doctor-Jack pot mine. —Gas enters this mine at nearly all points where there 
are open fissures and accumulates wherever the ventilation is defective. Owing 
to the closing of the Doctor shaft, the levels above 10 are'filled with the gas, which 
flows down the shaft to level 10. Here, however, it is carried out by ventilation 
through the stopes and the Advance No. 2 shaft. The 550-foot Morning Glory 
level was so filled with gas beyond the Doctor shaft as to be inaccessible at the 
time of visit. The gas appears to be chiefly carbon dioxide, probably mixed with 
nitrogen. It is said to be particularly troublesome on days when the barometer 
is low. 
The neighboring Mary McKinney mine is practically free from gas. 
