181)5.] Nature and Physiological Action of Black-damp. 253 



the lower. The time- marker indicates seconds. It will be seen that 

 the action of the black-damp became apparent after two inspirations 

 and attained its maximum after twenty inspirations, or one minute, 

 and that subsequently the hyperpnosa gradually became somewhat 

 less marked. 



After this observation the tap was turned full on and the brattice 

 closed, two of the party remaining outside in case of any accident. 

 A sample of air* taken at the moment when the last light (a candle 

 fixed horizontally) was extinguished, had the following composi- 

 tion : 



Oxygen 17'05 



Carbonic acid. . . 2'62 



Nitrogen 8O33 



Total 100-00 



or as compared with air.f 



Diminution in oxygen percentage 3'85 



Increase in carbonic acid percentage 2 '59 



nitrogen 1'26 



This composition corresponds to what would have been expected 

 from previous observations. Thus* in experiments by 'Dr. Lorrain 

 Smith and myself on air vitiated by respiration, J a match could no 

 longer be lighted when the air contained about 17"7 per cent, of 

 oxygen and 2'5 per cent, of carbonic acid, or 17'4 per cent, of oxygen 

 and 0'4 per cent, of carbonic acid. 



About half an hour later, Mr. "Warren's breathing had become 

 somewhat deeper than usual, though my own was not distinctly 

 affected. A sample of air taken at this point had the following com- 

 sition : 



Oxygen ,.. 15'30 



Carbonic acid 3"38 



Nitrogen 81'32 



Total 100-00 



or as compared with air 



Diminution in oxygen percentage 5'60 



Increase in carbonic acid percentage 3'35 



nitrogen 2 '25 



* The sample was taken close to, and at the level of, the candle, about midway 

 between the floor and the roof. .An upright candle and a safety lamp had already 

 gone out. 



f With the same gas-burette, used under the same conditions, pure air gave 

 20'90 per cent, of oxygen. 



J ' Journal of Pathology and Bacteriology,' 1892, 



