12 Biographical Memoir of the late Dr Henry. 



tractcd his attention 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 recent investigations. — " The property," he observes, "■ in- 

 herent 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 de- 

 gree of this attraction, rather than to any agency arising out 

 of their relations to caloric, that we are to ascribe the various 

 powers, which the gases manifest in that respect." 



An essay on the compounds of nitrogen, published in the 

 Manchester Memoirs for the same year (1824), though not 

 adding any facts of moment to the prior results of Gay Lussac, 

 yet made known some new and exact methods of speedily de- 

 composing nitrous oxide and nitrous gas. Thus the constitu- 

 tion by volume of nitrous oxide, was determined with singular 

 precision by detonating it with carbonic oxide, instead of with 

 hydrogen gas ; and nitrous gas was found to form an explosive 

 mixture with olefiant gas. 



It is worthy of remark, that all Dr Henry's scientific me- 

 moirs, which have been hitherto enumerated, are devoted to 

 the chemistry of aeriform bodies. For this refined department 

 of science, Dr Henry always manifested the strongest predilec- 

 tion. Indeed of nine experimental papers, contributed by him 

 to the Royal Society, no fewer than eight are dedicated to the 

 gases. At the period when Dr Henry's interest was first awak- 

 ened for philosophical pursuits, the rapid discovery by Priest- 

 ley of several new gases, and the sanguine hopes inspired by 

 Beddoes of detecting in these subtle and hitherto concealed 

 forms of matter powerful remedial agents, urged both physio- 

 logists and chemists to engage with ardour in pneumatic re- 

 searches. Subsequent experience has demonstrated, it is true, 

 the unsoundness of these projects for enriching with new re- 

 sources, the ai't of practical medicine. But the beautiful law, 

 unfolded by the genius of Gay Lussac, that the gases combine 

 in volumes which are either equal or multiples by an integral 

 number — by establishing, when interwoven with the Daltonian 

 philosophy, the existence of some simple relation between the 



