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equality of light from both burners, 5*36 cubic feet of coal 

 gas were equal to three cubic feet of naphthalized coal gas 

 which contained 200 grains of naphtha (s. g. 0'872). Such 

 were the quantities burned per hour. Hence 1000 cubic feet 

 of coal gas would require 6*511 imperial pints of such naph- 

 tha dissolved in itj in order to give a light which, in illuminat- 

 ing power, would be to that of mere coal gas as 25 to 14. 



" I ascertained that the gas which is generated so abundantly 

 during the destructive distillation of wood succeeds perfectly 

 for the purpose of illumination, when enriched with the va- 

 pour of naphtha or spirit of turpentine. During this distillation 

 two kinds of volatile spirit are produced ; one of them is well 

 known in commerce, it burns with a pale flame like alcohol ; 

 the other burns with a smoky yellow flame, highly luminous. 

 The latter, when purified, answers as well as coal naphtha 

 for the purposes here described. Some kinds of wood afford 

 so much as one-third of their weight of inflammable gas. It 

 is obvious how deserving these facts are of consideration in 

 countries where wood is abundant and coal scarce. 



'• It is, no doubt, in the recollection of many, that some 

 years since attempts were made to introduce gas condensed 

 in iron cylinders into public use, in Dublin and London ; and 

 portable gas companies were formed for the purpose of carry- 

 ing that object into effect. I need not now enter into the 

 nature of this project or the cause of its failure. I shall only 

 observe that, by simple methods, founded on the principles al- 

 ready described, it would have been very easy to insure suc- 

 cess. I have produced beautiful portable gas-lights, which 

 exceeded all others in steadiness and lustre, by introducing 

 bits of zinc, with a little dilute sulphuric acid, into a copper 

 cylinder, in all respects made like those of iron employed by 

 the portable gas companies. Hydrogen was not only gene- 

 rated, but, as there was no escape, it became highly condensed, 

 even to thirty atmospheres. By screwing on the valve a 



