254 Dr. J. Haldane. An Enquiry into the [Jan. 24, 



Neither of us could detect any loss of power, headache, or any 

 other abnormality, nor did we experience any trace of after-effect on 

 coming out of the mine. We did not continue these observations 

 further, as the vitiation was now evidently proceeding very slowly, 

 owing to the slight ventilation through the brattice cloth. When 

 this was lifted, the lights of the party outside were suddenly ex- 

 tinguished, so that the electric light alone remained ; and for some 

 time it was impossible to re-light a candle. 



The gas from the pipe had the following composition : 



Oxygen 9'60 



Carbonic acid 7'32 



Nitrogen 83'08 



Total 100-00 



or as compared with air 



Diminution in oxygen percentage 11 '30 



Increase in carbonic acid percentage 7'29 



nitrogen 4'01 



I could detect no trace of carbonic oxide, or of any gas yielding 

 carbonic acid on exploding the mixture, previously freed from 

 carbonic acid, with detonating gas. 



The calculated specific gravity of this mixture is 1'0258. A direct 

 determination was also made. A dry flask was filled directly from 

 the pipe, through drying tubes containing pumice and sulphuric 

 acid. The weight of the contained mixture at atmospheric pressure 

 and temperature was determined as against the weight of the same 

 volume of dry air at the same pressure and temperature. A similar 

 flask was used as a counterpoise in both weighings. 



The specific gravity as found was 1'0252. 



If we regard methane and air as accidental admixtures, and 

 calculate the air from the oxygen, the composition of the two speci- 

 mens of black-damp was as follows : 



No. 1. !Vo. 2. 



Methane 5'35 0"00 



r oxygen 1*45 9'60 



Air<| nitrogen 5'49 36'33 



L carbonic acid O'OO O'Ol 



Black-damp / ^ogen 7707 4675 



r I carbonic acid . . 10'64 7'31 



Total., 100-00 100-00 



