1 4,0 Dr. Henry on the aeriform compounds 
was indebted to Mr. Dalton, that it really has the proper- 
ties which have been ascribed to it by him as characteristic ; 
and in 1807 I found precisely the same characters in the fire- 
damp of coal-mines.* Dr. Thomson, also, from experiments 
in 1811,^ on the gas from stagnant water, and Sir Humphry 
Davy,J from the analysis of the fire-damp in 1815, drew 
the same conclusions. It is in the power, indeed, of every 
chemist to investigate for himself the properties and com- 
position of carburetted hydrogen gas, since it may easily be 
procured in considerable quantity, by stirring the bottom of 
almost any stagnant pool, especially if composed of clay. 
During the last summer, I obtained it from a source of this 
kind, which afforded it in such abundance, that several gal- 
lons might have been collected in a few minutes. This gas 
I submitted to repeated and most careful examination. It 
contained -^th its volume of carbonic acid, but no sulphu- 
retted hydrogen whatever, and no proportion of oxygen gas 
that could be discovered by attentively testing it with nitrous 
gas. The results of its combustion with oxygen gas, effected 
in a Volta's eudiometer in the usual manner, showed that it 
was contaminated with T-jth its volume of azotic gas. Apart, 
however, from this, the pure portion, in a great number of 
trials, required, as nearly as can be expected in experiments 
of this sort, two volumes of oxygen for combustion, and 
gave one volume of carbonic acid. Its specific gravity, 
taken on quantities procured at three several times, varied 
only from *582 to *58 6 , the mean of which is *584, ; and this, 
allowing for -J^th of azotic gas of specific gravity *972, 
* Nicholson’s Journal, 8vo. XIX. 149. 
f Mem, of the Wernerian Society, I. 506. J Phil. Trans. 1816, p. 5. 
