10 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 
Drainage and pumping have both shown that the underground water does not 
flow freely through the rocks in all directions. Neighboring mines in some cases 
show marked differences in water level, and the drainage tunnels on the west side 
of the district have but slightly benefited the mines on the east side. The behavior 
of the water shows that the unfissured breccia is practically almost impervious and 
that artificial drainage affects onty those parts of the district that are connected 
by fissures with the tunnel or shaft whence the water is drawn off. 
A movement is now in progress to begin a new drainage tunnel several hundred 
feet below the El Paso tunnel. Knowledge of the number of gallons of water cor¬ 
responding to a fall of 1 foot in the general reservoir would be of use in planning 
future operations. Mr. S. W. Mudd estimated that a discharge of 66,684,683 gallons 
corresponded to a general lowering of the water 1 foot. Mr. A. C. Jaquith estimated 
that in April, 1904, the discharge from the El Paso tunnel, corresponded to a lower¬ 
ing of the water 1 foot in the Elkton mine, was 34,839,775 gallons. The data on 
which Mr. Mudd’s estimate was based, however, are necessarily very incomplete 
and it is difficult to deduce, from the record of the Elkton, figures applicable to the 
entire area drained. The quantity of water drained for each foot of fall is likely to 
diminish with increase of depth, although it is probable that at a depth of 1,000 or 
1,500 feet below the El Paso tunnel open fissures and shattered zones in the breccia 
will still be sufficiently abundant to contain in the aggregate a large body of water. 
CHAPTER XIII.-UNDERGROUND GASES AND TEMPERATURE. 
Gases .—During the earlier years no unusual amounts of mine gases were noted, 
but as the workings deepened several properties began to be seriously inconven¬ 
ienced by a heavy gas which issued from the porous breccia or fine fissures. The 
principal sufferers have been the mines west of Battle Mountain and Bull Mountain. 
The gas has no smell or taste, but its presence is soon indicated by the fact that the 
candles refuse to burn and by several forms of physical distress among those who 
are obliged to work near the point where it issues.. A number of fatal cases of suffo¬ 
cation have occurred. The gas consists of a mixture of prevailing nitrogen with 8 
to 15 per cent of carbon dioxide and 5 to 10 per cent of oxygen. 
The gases carry much moisture and are warmer than the normal temperatures 
of the mines. The emanations are generally most copious when the barometric 
pressure is low, but they also exhibit fluctuations that are apparently independent 
of the state of the barometer. The gases are believed to be the last exhalations of 
the extinct Cripple Creek volcano. Probably the only effective way of combating 
the evil is by working under an air pressure slightly above the normal. 
Underground temperature .—Numerous observations in the mines lead to the 
conclusion that the average increment of underground temperature in the Cripple 
Creek district is about 1° F. for each 60 feet of depth. There is thus no special 
source of local heat that is likely to interfere with mining. As already mentioned, 
the mine gases have a temperature above that normal to the mines in which they 
occur. 
