RESPIRATION 31 1 



main was mistaken for a peculiar and rapidly infectious form of 

 typhus. No smell of gas was noticed at first, and the percentage 

 of CO must have been so low, and perhaps inconstant, that it took 

 some hours before any distinct symptoms of illness were produced. 

 At last the smell became noticeable, probably because the earth 

 through which the gas was escaping had become .saturated with 

 the odoriferous constituents, and so ceased to absorb them com- 

 pletely. 



Air of Mines. The air of mines is liable to be contaminated by 

 various gases known to British miners as black damp, fire damp, 

 afterdamp, white damp, and smoke. Of these, black damp is the 

 commonest and most universally present; fire damp is hardly 

 found except in connection with coal or oil; afterdamp occurs 

 only after explosions ; white damp in connection with spontaneous 

 heating of coal ; and smoke in connection with fires or blasting. 



Black damp is distinguished by miners through its character- 

 istic properties of extinguishing lamps without exploding and 

 not causing danger to life provided a lamp will still burn. As 

 ordinary black damp is heavier than air, it was formerly identi- 

 fied with COg. Its true composition was first ascertained in 1895 

 by Sir William Atkinson and myself.^ It is the residual gas of an 

 oxidation process, and thus consists of nitrogen with anything up 

 to about 21 per cent of carbon dioxide. It is now evident that 

 black damp may be formed by several different oxidation pro- 

 cesses, among which oxidation of timber, of coal, and of iron 

 pyrites (FeS2) are the most important. 



When timber oxidizes in the process of decay, it gives off 

 nearly as much CO2 as it consumes oxygen. Hence the black damp 

 formed consists of about 80 parts of nitrogen and 20 of CO2. 

 Freshly broken coal also oxidizes slowly for some time at ordinary 

 temperatures, but to a very limited extent. The oxidation process 

 is a simple chemical one and not dependent on microorganisms; 

 and extremely little CO2 is formed. In the oxidation of pyrites, 

 which is also a simple chemical process, no CO2 is directly formed ; 

 the sulphur is oxidized to sulphuric acid, which partly combines 

 with the iron to form ferrous and ferric sulphates, but may react 

 with calcium carbonate to form calcium sulphate, CO2 being of 

 course liberated. 



Black damp of one sort or another is found in practically all 

 mines, though in coal mines where there is much fire damp its 



*Haldane and Atkinson, Trans. Instit. of Mining Engineers, 1895. 



