256 Nature and Physiological Action of Black-damp. [Jan. 24, 



impending real danger from deficiency of oxygen. Were there no 

 carbonic acid in black-damp the danger would approach much more 

 insidiously, as hyperpno3a, &c., are not caused by de6ciency of oxygen 

 until real danger is imminent. Were black- damp ever carbonic acid, 

 or chiefly carbonic acid, as commonly supposed, the breathing would 

 with increasing* proportions certainly be markedly affected long 

 before the point at which lights are extinguished.* I have not been 

 able to obtain any account of gas met with in coal mines and possessing 

 the property of causing marked panting while at the same time 

 supporting a light. Panting is not mentioned as one of the symp- 

 toms produced by white-damp, nor has white-damp a high specific 

 gravity. 



Summary of .Conclusions. 



1. The specimens of black-damp consisted when undiluted of 

 nitrogen containing an admixture of a seventh to an eighth of its 

 volume of carbonic acid. 



2. Air containing just sufficient black-damp to extinguish a candle 

 or oil lamp produced no immediately sensible action on a man. A 

 mixture of about 16 per cent, of the black-damp and 84 per cent, of 

 air extinguished candles and lamps, whereas a mixture of about 

 60 per cent, of the black damp and 40 per cent, of air would be 

 required to produce immediate danger to life. 



3. The dangerous physiological action of black-damp is due to 

 deficiency of oxygen, not to excess of carbonic acid. The effect first 

 appreciable when increasing proportions of black-damp are breathed 

 is, however, due to carbonic acid alone. 



In conclusioD, I beg to express my hearty thanks to Mr. W. 1ST. 

 Atkinson for his co-operation in this investigation, and to the 

 managers of the Podmore and Lilleshall Collieries for their courtesy 

 in doing everything possible to facilitate the work. 



Note. Added January 7, 1895. 



Since writing the above I have examined a specimen of black- 

 damp from an ironstone pit (communicating with a seam of coal) at 

 Apedale. A double analysis of the sample gave the following 

 results : 



No. 1. No. 2. 



Oxygen 10'07 10'09 



Carbonic acid 7'64 7'60 



Nitrogen 82*29 82%31 



Total 100-00 100-00 



* An experiment demonstrating this fact is described by Dr. Lorrain Smith and 

 myself. Loc. cit. 



