72 



CONTRIBUTIONS TO THE KNOWLEDGE 



to make it most favourable for their development; but no 

 new principle has been applied to the generating process, and 

 although the attempts above alluded to have been attended 

 with some success, yet it is evident from Dr. Henry's descrip- 

 tion of the quantity and quality of gases obtained from 

 coal and cannel, which was laid before this society in 1819, 

 that little has been gained either as regards the quantity of 

 gas obtainable from a given weight of coal or its illuminating 

 power. Our knowledge of the constituents of coal gas has 

 also been very little extended, although our means of gaseous 

 investigation have been greatly increased by the labours of 

 Bunsen, Kolbe, Regnault and others, in perfecting the me- 

 thods employed in the analysis of gases. 



Under these circumstances, I venture to hope that the 

 observations contained in the following pages, imperfect as 

 they are in many respects, may not be altogether unaccept- 

 able as contributions to our present knowledge of this very 

 important branch of manufactures. These observations 

 derive their origin from an extensive series of experiments 

 just concluded, which I made at the request of two merchants 

 of this town, upon a new process of gas manufacture known 

 as White's Hydrocarbon process, of which I believe the 

 members of this society are not entirely ignorant. In detail- 

 ing these experiments and the conclusions arising from them, 

 I shall endeavour as much as possible to eschew the commer- 

 cial relations of the subject, and confine myself to points of a 

 strictly scientific character. 



The usual process of gas-making consists, as is well known, 

 in exposing coal or cannel to a red heat in close vessels of 

 convenient size and shape, until all, or the greater part of the 

 volatile matter is expelled. Coke is the material left in the 

 retort, and the matters volatilized consist of condensible 

 vapours, and permanent gases more or less saturated with 

 these vapours. It does not appear that the quantity of coke 

 obtained from a given weight of coal is liable to any import- 



