SUBTERRANEAN GASES. 
253 
A loss of oxygen by oxidation of pyrite or organic matter, for instance, soon 
makes air unfit for respiration. Air having but 15 per cent of oxygen is dangerous 
or even fatal. 0 
The percentage of carbon dioxide given in the table is often exceeded. Accord¬ 
ing to Cl. Winkler, the exhaust air in the Saxon coal mines averages 0.7 per cent 
C0 2 , but with such an amount the air is still respirable. At 1 per cent the presence 
of C0 2 may produce no special discomfort. With 2 to 2.5 per cent C0 2 the candles 
are extinguished, 6 but, as all miners know, the air can then still be breathed without 
much inconvenience. At 5 or 6 per cent the condition is very dangerous, and any 
excess of C0 2 above this amount is soon fatal. 
The per cent of carbon dioxide may be easily determined in the mine by the 
little portable apparatus devised by Lunge, by which the volume of air which will 
neutralize a given amount of lime water is ascertained, the end of the reaction being 
indicated by the discoloration of a solution of phenol-phtlialein. Such an appa¬ 
ratus is in regular use by the mine inspectors in the alluvial mines of Victoria, 
Australia, and one of these was obtained through the kindness of Mr. Wykeham 
Bayley of the government laboratories in Melbourne. It was soon found to be use¬ 
less, however, for in the Cripple Creek mines the excess of nitrogen may be as dan¬ 
gerous as that of carbon dioxide. Unfortunately no methods for the direct deter¬ 
mination of oxygen are suitable for a compact portable apparatus, and thus physio¬ 
logical effects, together with candles and lamps, afford the only easy and safe method 
of ascertaining the deficiency in oxygen. It was found that the small portable 
acetylene lamp now in common use among mine superintendents and engineers 
offers a fairly safe indication. This lamp will burn long after the candles are extin¬ 
guished, but when it refuses to burn the air is very dangerous. This probably 
indicates about 15 per cent of oxygen. 
Neither nitrogen nor carbon dioxide is directly poisonous, and the effect is in 
both cases due to suffocation. But there is reason to believe that the heavy carbon 
dioxide produces the worse effect by interfering more actively with the diffusion of 
gases in the lungs. It is difficult to say just what deficiency in oxygen may be per¬ 
missible in spaces where men are working continuously. It assuredly should not 
exceed 1 per cent. The air may, of course, be entirely unfit for long-continued use 
while candles are still burning. In general the workings of the Cripple Creek mines 
are well ventilated and contain a very small percentage of carbon dioxide. 
DISTRIBUTION AND MODE OF OCCURRENCE. 
The gas appears chiefly in the western part of the district, where few of the deep 
mines are entirely free from it. It rarely occurs in the eastern part, including the 
mines of Victor and Battle Mountain and the Vindicator and Isabella vein systems, 
although these mines are among the deepest in the district. A little gas may occur 
sporadically in long crosscuts, or small pockets of it may be struck (as in the Hull 
City mine), but as a whole this vicinity is remarkably exempt from it. In this con¬ 
nection it is worthy of note that the veins mentioned form a separate drainage sys- 
a Kohler, O., Lehrbuch der Bergbaukunde, Leipzig, 1900, p. 674. 
b Smith, A. M.. Report on the foul air in the Allendale mines: Special Rept., Dept, of Mines, Melbourne, 1892. 
13001— No. 54—06-18 
