TRANSACTIONS OF THE SECTIONS, 

 niuminating-po-w-er of Gas from Coals in lbs. of Sperm. 



71 



Average percentage of increase in illuminating-power 7-57, or -^ of whole light. 

 The increase in illuminating-po-wer is undoubtedly due to tbe presence of a larger 

 proportion of the heavy hydrocarbons, as the condensation by bromine rose in 

 each trial on an average of one per cent, of increase. The larger proportion of the 

 heavy hydrocarbons may probably arise from several causes : — 



(1) The intermixture of the lighter gases of the inferior coals -with the heavier 

 gases of the better coals, thus tending to save the heavy hydrocarbons from being 

 decarbonized or reduced by the heat of the retort. 



(2) The mixture of the lighter gases -svith the heavier gases and vapours, tending 

 to teep the latter from separating in the condensers, pm-ifiers, and gasholder ; and 



(3) Probably also the reaction of tbe gaseous bodies upon each other during the 

 moment of their liberation from the coals by destructive distillation, and when the 

 gases are in the condition kno-wn as that of the nascent state, and "when, as is -svell 

 tno-wn, chemical reaction is most energetic. 



In England so much attention is paid to coke that necessarily the quality of the 

 resultant fuel obtained from the mixtures of coals must be considered. In all the 

 experimental trials referred to in this paper the mixed coke -was at least of fair 

 quality. The general results of the inquiry therefore is, that, given a certain quan- 

 tity of coals of different gas-producing po-wers, it is more economical to mix these 

 coals, and thereafter heat the mixture m the same retorts, than to distil each coal 

 separately in different retorts, and thereafter mingle the gases in the ordinary -way. 



