MEMOIR OF THE LATE DR. HENRY. 117 
constitute a distinct gaseous species, that olefi- 
ant gas is the only known compound of carbon 
and hydrogen; and that the gases obtained from 
oil and coal are nothing more than mixtures of 
olefiant with simple hydrogen. 
In an elaborate paper published in the Tran- 
sactions for 1821, Dr. Henry succeeded, how- 
ever, in establishing the soundness of his original 
views. He contended that the concurring re- 
sults obtained by Dr. Dalton, Sir H. Davy, Dr. 
Thomson and himself, from the analysis of 
carburetted hydrogen collected both from stag- 
nant water and from the coal measures, at dis- 
tant times and places, clearly demonstrate that 
gas to be a true chemical compound, character- 
ized by perfect uniformity of properties and 
composition. He proceeded to investigate the 
action of chlorine both upon carburetted hydro- 
gen and olefiant gases, with a view to learn how 
far chlorine may be depended upon as a means 
of effecting their separation. Carburetted hy- 
drogen was found to be wholly unaltered by 
prolonged contact with chlorine, when light was 
carefully excluded. Under the same circum- 
stances olefiant gas on the contrary was entirely 
removed by chlorine. Hence he derived a sim- 
ple and beautiful mode of separating olefiant gas 
