of charcoal and hydrogen . 1 39 
different proportions , the greater proportions are multiples of the 
less by an entire number. 
A different view of the subject has lately been taken by 
the ingenious author of the Bakerian Lecture, published in 
the Philosophical Transactions for 1820. In that paper, Mr. 
Brande has endeavoured to prove, that the gas called light 
carburetted hydrogen, or simply carburetted hydrogen, or 
hydro-carburet, is not entitled to be considered as a distinct 
species ; that the only aeriform compound of charcoal and 
hydrogen, which is with certainty known to exist, is the gas 
called olefiant, or bi-carburetted hydrogen; and that the 
gases evolved by heat from coal and oil, are in fact nothing 
more than mixtures of olefiant and simple hydrogen gases 
in various proportions. 
In assuming, in the first Essay, the existence of light 
carburetted hydrogen as a definite compound, characterized 
by its requiring, for the complete combustion of each volume, 
two volumes of oxygen, and giving one volume of carbonic 
acid, I relied on the sole authority of Mr. Dalton ; for the 
gas of marshes, though before known to be inflammable, 
had not been subjected to accurate examination by any other 
chemist. Mr. Cruickshank, indeed, speaks of it as “ pure 
hydro-carbonate;”* but since he classes it in that respect 
with the gas obtained by the destructive distillation of cam- 
phor, from which it differs essentially in composition, it is 
plain that he was not correctly acquainted with the proper- 
ties of pure carburetted hydrogen. Previously to the second 
set of experiments, I satisfied myself by the careful analysis 
of a specimen of the gas from stagnant water, for which I 
* Nicholson’s Journal, 4*0. vol. V. p. 6 . 
