44 Mr. Ricardo's Reply to Mr. Low [July, 



Article VII. 



Remarks on Oil and Coal Gas, in answer to Mr. Low and 

 " A Subscriber:' By M. Ricardo, Esq. 



(To the Editor of the Annals of Philosophy.) 



I must again request your insertion in the Annals, of a few re- 

 marks on a paper by Mr. Low, in the Philosophical Magazine of 

 April last, which is a reply to my former statement respecting the 

 comparative advantages of oil and coal gas. I will endeavour, 

 for my own and your readers' sakes, to be as concise as possible, 

 and to do no more than correct the statements, or rather mis- 

 statements, of that gentleman. 



He begins by calling in question my correctness as to the 

 quantities of light produced from oil and coal gas. In reply 

 to his observations on this point, I need do little more than refer 

 him to the excellent and truly philosophical paper by Dr. Henry, 

 which was read before the Royal Society, and has since been 

 printed. It ;s there shown, as was known before, by those accus- 

 tomed to oil gas, that a very great difference exists in it, according 

 to the mode in which it is prepared ; how very much inferior the 

 average of what he procured was to that which was furnished him 

 by yourself, from an apparatus of Messrs. Taylor; and, again, 

 how superior the latter was to the coal gas obtained from Wigan 

 coal, which, in a former paper, he proved to be one-third better 

 than that produced from common coal. From Dr. H.'s experi- 

 ments on the combustion of these gases by oxygen, taking 

 the average of the specimens he obtained from Messrs. Taylor, 

 and the average of the coal gas he obtained at one hour, and 

 at five hours, it will be found that the former contained 40 

 per cent, of that peculiar gas, from which these gases derive 

 the chief of their illuminating power, and Wigan coal gas 

 10 per cent., and that, from common coal only 6-*-. Thus 

 it is not only possible, but highly probable, that the gas which 

 Dr. Ure tried, and whose testimony forms so triumphant a note 

 to Mr. Low's paper, was of a quality similar to that produced 

 by Dr. Henry, and very unlike that from Messrs. Taylor's 

 apparatus. These gentlemen have been for many years em- 

 ployed in bringing their apparatus to perfection ; and how far 

 they have succeeded, no other testimony need be quoted than 

 that to which i have referred. It is needless to remark that 

 my experiments were tried with gas procured from a similar 

 one, and that the results of a number of them, tried in va- 

 rious ways, were invariably the same. A single jet dame, is- 

 suing from an orifice of the 60th of an inch in diameter, and 

 TV inch high, gave a light equal to one mould tallow candle, 



