404 Mr, Dewey on Gas Illumination, [Dec. 



In the course of my investigfttions, I found opinions much at 

 variance on the subject of the ilhiminating powers of the two 

 gases, and I could not form an opinion at all satisfactory. To 

 put the matter at rest, I proposed to Messrs. Taylor and Marti- 

 neau to find a situation where the main pipes from coal gas and 

 oil gas works run parallel to each other, and to bring the gases, 

 as they were supplied to customers, into the same room, and 

 burn them together. They found such a situation in the 

 Whitechapel-road, and had them brought together, and the 

 burners supplied through two accurately adjusted meters, made 

 by Mr. Crossley, and who with Dr. Arnot, Mr. Preuss, and 

 yourself, were invited to assist us ; and Mr. Crossley kindly 

 undertook to manage the meters that no mistake might occur. 

 The coal gas was supplied from the mains of the Imperial Gas 

 Works, and the Oil Gas from that at Bow. We then proceeded 

 to make the experiments on two separate evenings. 



The specific gravity of the two gases was found to be, of coal 

 gas 0*4069,* of oil gas 0*9395 ; and the average consumption per 

 hour (being the mean of seven experiments, and which varied 

 but slightly from each other), coal gas 4*850 feet, oil gas 1'368 

 feet. The flames were adjusted so as to give aUght of equal in- 

 tensity. I have seen more than 100 feet of gas obtained from a 

 gallon of good clean whale oil, and am confirmed in the opinion 

 that about that average can be obtained, from an inspection of 

 the books of four oil gas works. Oil gas has been objected to on 

 account of its price. This must be owing to the opinion that one 

 foot of oil gas does not contain as much illuminating matter as 

 about three and a half feet of ordinary coal gas. But it does. 

 I would not be satisfied till I had tried it, nor with one night's 

 experiments. And was it not so, and suppose it to cost much 

 uiore, which I do not admit where oil is cheap, and coals dear, 

 I know no good reason that some people should not wear 

 auperfine, though the great mass of the world are satisfied with 

 Jine; and they will use superjine oW gas, and pay for it, most cer- 

 tainly, if they can obtain it as cheaply as faie coal gas. The 



* These results coincide very nearly with those obtained a few months since by 31. 

 Faraday and myself, on comparing the specific gravity and illuminating powers of the 

 two gases at Messrs. Hawes' and Co. soap work. The oil gas was manufactured on 

 their premises, and the coal gas was obtained from a neighbouring establishment. 

 Its lightness sufficiently proves that it was uncontaniinated by any accidental admixture. 

 I shall give at one view the results obtained at both places. 

 At M(4>srs. Hawes'. 

 Coal gas. Oil gas. 



Specific gravity 0.4291 0.9657 



Illuminating power 1. .3.567 



So that one cubic foot of oil gas is equal to rather more than SJ feet of coal gas. 



At \\^Tiitechapel. 

 Coal gas. Oil gas. 



Specific gravity 0.4069 0.9395 



Illuminating power I . 3.54 1 



It will be observed, that in the latter case, although both gases were specifically lighter 

 than in the former, their comparative illuminating power is nearly similar.— iirfj/* 



