208 brs. Christison and Turner on Oil and Coal Gas. 



specific gravity of the gas will not exceed 600. And in such 

 a town as London, where the cannel coal can scarcely be pro- 

 cured at all, the average specific gravity will not exceed 450. 



The average specific gravity of oil gas should eventually be 

 the same every where. It is difficult to ascertain what the 

 average is at present, as made by large establishments ; but 

 there is no substantial cause why it should fall short of 920. 

 We have assigned strong reasons, however, for believing that 

 it must be soon improved considerably. This improvement 

 indeed may be no great gain ; for the question will then occur, 

 whether it can be effected without diminishing the quantity of 

 gas in the same proportion with its increase in quality. It is 

 generally supposed that an improvement in the quality of oil 

 gas is necessarily attended by a loss in {|aantity; but, so far 

 as can be discovered, this idea rests on experiments performed 

 by operatives only, whose authority we are satisfied, from re- 

 peated observation, can by no means be relied on. If char- 

 coal is left in the retorts at the end of each charge, it is clear 

 that the gas may be improved by the addition of all this char- 

 coal, without any diminution in quantity; for if it be added to 

 the light carburetted hydrogen, which gives little light, so as 

 to convert it into the olefiant gas, which is powerfully illumi- 

 nating, the change, it is well known, will take place without 

 any alteration in volume. On the other hand, if good oil gas 

 be exposed to a high temperature, it is partly decomposed, and 

 deposits some of its charcoal. Part of the olefiant gas becomes 

 light carburetted hydrogen, and without any increase in vo- 

 lume; for the volume is not increased unless it is resolved into 

 charcoal and hydrogen. Hence a bad gas may be made from 

 oil, which shall not exceed in quantity the good gas of Taylor 

 and Martineau. And in point of fact, we have several times 

 found, when the retorts were choked with charcoal, and the 

 specific gravity of the gas was only 660, that the quantity fell 

 short of 100 cubic feet per gallon, which is said to be about 

 the average produce when the gas is good. When oil gas has 

 a specific gravity of 910, charcoal is still found in the retorts. 

 It may therefore be improved by the addition of all this char- 

 coal, and still retain its volume. Besides, it may be possible 

 to improve it by the addition of charcoal from other sources. 

 Hence, while we at present assign to oil gas the average spe- 

 cific gravity of 920, we cannot help anticipating a considerable 

 improvement and positive gain. 



From what has been said of the average quality of coal gas 

 in different quarters of the kingdom, it is clear that the ques- 

 tion of its ceconomy, compared with oil gas, can be only an- 

 swered relatively. In Edinburgh and Ghisgow, where coal is 

 moderately cheap, and coal; gas of good quality, oil gas must 



