120 MEMOIR OF THE LATE DR. HENRY. 
proportions thus ascertained of its constituents, 
was .303, a number coinciding as nearly as 
could be expected with the actual specific gra- 
vity of the gas .308. 
In the course of this enquiry, Dr. Henry 
noticed the curious property of gaseous inter- 
ference, which was observed about the same 
time, and first made public by Dr. Turner. 
Though not affecting the main object of his 
researches, these phoenomena attracted his at- 
tention by their singularity and novelty; and 
the experiments, he performed in the hope of 
unfolding their nature, suggested a theory of 
interference, which has been confirmed by re- 
cent investigations——“The property,” he ob- 
serves, “inherent in certain gases, of retarding 
the action of the platina sponge, when they are 
added to an explosive mixture of oxygen and 
hydrogen is most remarkable in those, which 
possess the strongest attraction for oxygen; 
and it is probably to the degree of this attrac- 
tion, rather than to any agency arising out of 
their relations to caloric, that we are to describe 
the various powers, which the gases manifest 
in that respect.” 
An Essay on the Compounds of Nitrogen, 
