118 MEMOIR OF THE LATE DR. HENRY. 
from the other gaseous compounds of carbon 
with hydrogen or with oxygen, as well as from 
pure hydrogen. After establishing the perfect 
accuracy of this process, on artificial mixtures 
of the gases in known proportions, he applied it 
to the mixtures of the same gases in unknown 
proportions, which constitute oil and coal gases. 
The best oil gas showed forty per cent of a gas 
condensible by chlorine; the best coal gas not 
more than thirteen per cent. The residuary 
gases, left after the complete action of chlorine, 
were then detonated in a volta tube with oxygen, 
and afforded results, showing that they were 
mixtures of carburetted hydrogen, carbonic 
oxide and hydrogen gases, in proportions which 
he was then unable to determine except by 
approximative calculation.—‘“‘No one instance, 
he concludes “has ever occurred to me of a 
gas obtained from oil or coal, which after the 
action of chlorine upon it, with the exclusion of 
light, presented a residuum at all approaching 
to simple hydrogen gas.” 
In his latest communication to the Royal 
Society, (1824) Dr. Henry succeeded in con- 
quering the only remaining difficulty in the 
analysis of these complex mixtures; viz., the 
ascertaining by chemical means, the exact pro- 
