which are evolved in Coed-Mines. 149 



lesweiler pit-gas, that the quantity of defiant gas, when calcu- 

 lated from the quantity of carbonic acid formed, was greater 

 than that afforded by direct determination by means of chlo- 

 rine. The same was the case in the analysis of both the other 

 pit-gases. 



Professor Johnston*, when communicating an account of his 

 examination of a fossil wax which occurs in cavities in the 

 coal-pit of Urpeth near Newcastle-upon-Tyne, and which bears 

 a great resemblance to the ozocerite, or ozokerit, found in large 

 quantity in Moldavia, proposes the hypothesis that that sub- 

 stance, emitted in the form of vapour from the coal-strata, and 

 carried along by the lighter gas (fire damp) given off at the 

 surface, was partly condensed in the cavities and other cooler 

 places with which it came in contact. Since there are so many 

 hydro-carbons which, for the most part, are isomeric with ole- 

 fiant gas (and more are daily discovered), this hypothesis has 

 some probability. But it is very improbable, that in an in- 

 flammable gas, such inflammable vapours ever occur, as are 

 produced by the decomposition of oil and other similar sub- 

 stances by means of heat. We have much rather reason to 

 suppose, that these inflammable gases are formed in the same 

 way as the inflammable gas of marshes. 



I am of opinion that not only the inflammable vapours 

 pointed out by Faraday, but also carbonic oxide gas, are pe- 

 culiar to inflammable gas produced by heat. If these com- 

 ponent parts are found in any inflammable gas, we may con- 

 clude as to its having been produced by heat ; if we do not 

 find them, we may assume that the inflammable gas has been 

 formed in the same manner as the marsh-gas, that is, in the 

 moist way. 



Experiments to determine the limits of the inflammability of the in- 

 flammable pit-gases mixed with atmospheric air. 



These experiments possess a practical rather than a theo- 

 retical interest, inasmuch as they shew in what relations the 

 inflammable gas must be united with atmospheric air in order 



* London and Edinburgh Philosophical Magazine, 3d series, vol. r.ii. 

 p.3J59. 



