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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 6'5 11 imperial pints of such naph- 

 tha dissolved in it, 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 thegas 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 afl"ord 

 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 efi'ect. 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 



