400 Mr. Johnston's Description and Analysis of Hatchetine*, fyc. 



appears that several of them should be occasionally present in the air which 

 circulates through mines of bituminous coal. 



The common fire damp requires, for its perfect combustion, ten times its 

 bulk, the vapour of Faraday's light liquid thirty times, and that of naphtha 

 forty-five times its bulk of common air. A very small portion of either of 

 the latter, therefore, would render an atmosphere dangerous. The sudden 

 outburst of a small reservoir of any one of the more dense forms of this 

 compound of carbon and hydrogen would pollute a working previously 

 considered safe, and give rise to an explosion where none was considered 

 possible. In a district of country like the north of England, where rich 

 bituminous coal is so abundant, where mines are worked at the very verge 

 of the inflammable state, and where the most serious accidents from explo- 

 sions occasionally occur, it is of importance, I think, that the probable pre- 

 sence of such substances, in the state of vapour, should be taken into ac- 

 count. Where the coal is richer than usual, and where troubles occur in 

 which these compounds, as at Urpeth, may exist in a liquid or solid state, 

 a more rapid escape of combustible matter may be anticipated, while the 

 probability of such escape affords a rational explanation of those sudden 

 and unexpected emissions of gaseous matter which have occasionally been 

 followed by consequences so disastrous. 



Durham, August, 1837. 



