Page:Experimental researches in chemistry and.djvu/184

1825.] hydrogen gas will send up such a vapour; and that he has been informed, that when oil-gas was condensed in Gordon's lamp, it deposited a portion of highly volatile oil.

A writer in the 'Annals of Philosophy,' N. S. iii. 37, has deduced from Dr. Henry's experiments, that the substance, the existence of which was pointed out by Mr. Dalton, was not a new gas sui generis, "but a modification of olefiant gas, constituted of the same elements as that fluid, and in the same proportions; with this only difference, that the compound atoms are triple instead of double:" and Dr Thomson has adopted this opinion in his 'Principles of Chemistry' This, I believe, is the first time that two gaseous compounds have been supposed to exist, differing from each other in nothing but density; and though the proportion of 3 to 2 is not confirmed, yet the more important part of the statement is, by the existence of the compound described at page 163; which, though composed of carbon and hydrogen in the same proportion as in olefiant gas, is of double the density

It is evident that the vapour observed by Mr. Dalton and