86 



CONTKIBtJTIONS TO THE KNOWLEDGE 



hydrogen and carbonic oxide gases ; and second, the decom- 

 position of steam by charcoal, with the formation of two 

 volumes of hydrogen and one volume of carbonic acid. 



The mixture of hydrogen, carbonic oxide, and carbonic 

 acid along with a large excess of steam, then passes into the 

 resin retort, where, mixing with the decomposing resin 

 vapour, it twice traverses the whole length of the red hot 

 vessel. There is no doubt that the greater portion of water 

 gas is produced by the decomposition of this excess of steam 

 in the resin retort, since the weight of charcoal required for 

 the formation of the volume of water gas generated in each 

 of the above experiments, is more than twice as great as that 

 which disappeared from the water retort. This circumstance 

 elucidates the advantages arising from the passage of this gas, 

 mixed with steam, through the resin retort; the fuligenous 

 matter, which would otherwise accumulate and block up this 

 retort and its pipe, as is well known to be the case when 

 resin alone is used, is converted into permanent combustible 

 gas; this, although possessing no illuminating power, yields 

 valuable service in rapidly sweeping out of the red-hot 

 retort the permanent illuminating gases produced by the 

 decomposition of the resin, and in saturating itself with the 

 various volatile hydrocarbons, upon which so much of the 

 illuminating power of all gas depends, and which would 

 otherwise, to a great extent, be left behind with the tar and 

 water in the condensers. It is well known how rapidly 

 olefiant gas and all rich hydrocarbons are decomposed into 

 charcoal and gases, possessing little or no illuminating power 

 when in contact with the walls of a red-hot retort, and 

 therefore the value of the water gas in thus rapidly removing 

 them from this destructive influence, and retaining them in 

 a permanently gaseous form, can scarcely be over-rated ; 

 indeed, this principle has not been entirely neglected in the 

 manufacture of coal gas by the old process, several companies 

 having attached exhausters to their retorts, which, however, 



