58 F. B. GUTHRIE AND A. A. ATKINSON. 



The work was again resumed and completed without further 

 mishap. On the 10th August, 1900, the mine was reopened, 

 prior to which the following samples had been collected from the 

 stopping by means of pipe with tap : — 

 No. Time of collection. Carbon dioxide. Oxygen. Nitrogen. 



1. 11-15 a.m. 1-46 15-88 82-66 



2. 11-30 „ 1-04 16-93 82-03 



3. 1210 „ 209 13-68 84-23 



4. 12-20 „ 1-45 15-79 82-76 



Carbon monoxide was absent in all samples, and also all inflam- 

 mable gases. Sample No. 2 supports combustion, but the others 

 do not. Prof. Clowes 1 states that air becomes extinctive to a 

 candle when diluted with nitrogen, until the oxygen is reduced to 

 16*4%. This agrees well with the above observations in which 

 only No. 2 with 16*92% oxygen was capable of supporting com- 

 bustion. The carbon dioxide has little or no effect in the 

 extinction of flame, in the proportions in which it is present in 

 the above. 



It may here be of interest to discuss the effects of the diminution 

 of oxygen and the presence of different proportions of C0 2 and of 

 black damp upon respiration and lights. By black damp is under- 

 stood 2 the residual gas produced by the oxidation of coal. This 

 has according to Dr. Haldane a fairly constant composition of 

 13 per cent. C0 2 and 87 per cent. N. 



A candle flame is extinguished in an atmosphere consisting of 

 oxygen and nitrogen only, when the percentage of oxygen is 

 reduced to between 16 and 17 per cent. This mixture can, how- 

 ever, be breathed by a man without any ill effects, and it is not 

 until the oxygen percentage has fallen to about 12 that the breath- 

 ing becomes affected. According to Dr. Haldane 3 the breathing 

 becomes deeper and more frequent, and the face bluish when the 

 oxygen content is diminished to 9 per cent., at 5 per cent, loss of 

 consciousness follows and death. 



1 Proc. Eoy. 3oc, 1894, Vol. lvi., p. 2. 



2 Haldane— Trans. Fed. Min. Inst.. Vol. vin., p. 549, etc. 



3 Report on causes of death in Colliery Explosions, etc., 1896. 



