110 



CONTBIBUTIONS TO THE KNOWLEDGE 



the gas obtained from the same coals by the ordinary process 

 of manufacture, and in some cases it is even less than that 

 produced by a pure coal gas flame giving an equal light. 

 The following table shows this comparison: — 



The favourable position which the gases made by the new 

 process occupy in the above comparison, could not have been 

 attained if the whole or even a very large portion of the 

 water gas had been generated in the charcoal retort; for 

 when water gas alone is so generated, it is found to consist 

 of hydrogen and carbonic oxide, mixed with quantities of 

 carbonic acid, varying from to 15 per cent, according to 

 the heat employed and other circumstances. When the per 

 centage of the acid gas is 0, then the volumes of hydrogen 

 and carbonic oxide are equal ; and as no important quantity 

 of carbonic acid was ultimately present in the gases produced 

 in the foregoing experiments, the whole of that gas entering 

 the coal retort must be converted into carbonic oxide, and 

 therefore we may consider the water gas entering the coal 

 retort as being composed of equal volumes of hydrogen and 

 carbonic oxide. Now, if the increase in the total quantity of 

 gas produced by the application of the new process to any 

 given coal or cannel, were due only to the water gas formed 

 ill the charcoal retort, it is obvious that the gain in carbonic 



