424 Experiments on the Gas from Coal. 
full state of expansion would be 200 mea- 
sures, as determined by the fact, that oxygen 
gas uniformly takes for saturation double its 
volume of hydrogen gas, and no other pro- 
portion. 
Nature of the Gas from Coal. 
The opinion which I formerly advanced 
on this subject,* though opposed by writers 
of so much authority as M. Berthollet and 
Dr. Murray, still appears to me to be much 
more probable, than that the varieties of 
gas from inflammable substances, which may 
be almost infinitely diversified by modifica- 
tions of temperature, are, as those philoso- 
phers suppose, so many distinct compounds 
of hydrogen and charcoal, or of hydrogen 
and charcoal in combination with oxygen. 
The reasons that induce me to abide by my 
original view of the subject are the follow- 
ing: . 
1. We are acquainted with two distinct 
and well characterized compounds of hydro- 
gen and charcoal, in one of which a given 
weight of charcoal is united with a certain 
quantity of hydrogen, and in the other with ~ 
double that quantity. Besides these two, no 
* Nicholson’s Journal. 8yo, xi. 68. 
