COMBUSTIBILITY OF GASES. 
S3 
its expansive force it would, no doubt, oppose the union of 
•hydrogen and oxigen, an insurmountable impediment, if the 
resistance of the atmosphere did not exercise a reaction which, 
under certain circumstances, becomes a maximum of compres- 
sion. 
7. All these facts, joined with those of my former Memoir, General thee* 
may establish the following theorem : rem ° 
Hydrogen gas in the atmosphere, under a pressure of four or 
five times that of the ordinary state of the lower air, is not 
capable of being set on fire by the electric spark, nor by a 
lighted canule, whether that dilatation be owing to a diminished 
pressure, or a more elevated temperature. 
I take the extreme limit of dilatation here as it was ob- The limits ©f 
served in my experiments with hydrogen 23s and common air. dilatation will 
_ . , , , J & vary with the 
But there is no doubt that the two gases, if mixed m a propor- proportion of 
tion less favourable to combustion (as for example, two or component 
three parts of hydrogen to one of air) would not require so P aUbc 
great a dilatation to deprive them of the faculty of inflamma- 
tion. Hence it may happen, that at the bottom of the salt 
mines of Cracovia, or at Amsterdam, or any other low town, 
it might be found, that a gaseous mixture might be inflammable, 
which would not be so at a more elevated town, such as Quito, 
in South America. This would depend on the proportion in 
which the hydrogen might be mixed with the atmospheric 
air. 
8. Various phenomena may be, without difficulty, explained Explanation 
from this theory, of which I shall give a few- examples. fmm^this^o^ 
A great number of combustible bodies inflame on passing trine, 
in the state of oxide into the oxymuriatic gas.. Much more 
would it, therefore, follow, that the oxymuriatic gas would be 
decomposed by charcoal at an elevated temperature. Never- 
theless, M. Tlienard and Gay Lussac have lately discovered, 
that oxymuriatic gas may be passed through ignited charcoal 
without the gas being decomposed. 
Interesting and instructive as this experiment may be in Oxymnr. gas 
itself, as to its explanation, I do not accede to the opinion of 
these chemists on that head. According to their reasoning, lighted char- 
the oxymuriatic gas is decomposed only^-when it meets with coal * 
hydrogen or water ready formed. For my part, I am per- 
suaded, that the presence of water is an indispensable condi- 
Vol. XXXV.— No. 161. D tion 
