HENRY. 



59 



ither, was yet marked by several important contributions 

 to science. Tn 17'J7 he communicated to the Royal Society an 

 experimental memoir (the first of a long series with which he 

 enriched the ' Transactions' of that body), the design of which was 

 tn iv-r>st;il>lish the title of carbon to be ranked among elementary 

 bodies, which had been denied by Austin, Beddoes, and other 

 eminent clu-mists. In this paper he subsequently discovered a 

 fallacy in his own reasoning, which he exposed before it had been 

 detected by any other chemist. In 1800 he published in the ' Philo- 

 sophical Transactions' his experiments on muriatic acid gas, and in 

 1803 made known to the Royal Society his elaborate experiments 

 on the quantity of gases absorbed by water at different temperature 

 and under different pressures, the result of which was the establish- 

 ment of the law that " water takes up of gas, condensed by one, two 

 or more additional atmospheres, a quantity which would be equal to 

 twice, thrice, &c. the volume absorbed under the ordinary pressure 

 of the atmosphere." In 1808 Henry was elected a Fellow of the 

 Royal Society, and in the same year described in their ' Transactions' 

 a form of apparatus adapted to the combustion of larger quantities 

 of gases than could be fired in eudiometric tubes. This apparatus, 

 though now superseded, gave more accurate results than had ever 

 before been attained. In the following year (1809) the Copley gold 

 medal was awarded to him for his valuable contributions to the 

 * Transactions ' of the Royal Society. For the next fifteen years 

 Dr. Henry continued his experiments on gases, making known to 

 the Society the results from time to time. In his last communica- 

 tion, in 1824, he claimed the merit of having conquered the only 

 difficulty that remained in a series of experiments on the analysis of 

 the gaseous substances issuing from the destructive distillation of 

 coal and oil viz., the ascertaining by chemical means the exact 

 proportions which the gases, left after the action of chlorine on oil 

 and coal gas, bear to each other. This he accomplished by skilfully 

 availing himself of the property (recently discovered by Dobereiner), 

 in finely divided platinum, of causing gaseous combinations, and he 

 was thus enabled to prove the exact composition of the fire-damp 

 of mines. All the experiments of Dr. Henry which have been 

 previously alluded to bore upon aeriform bodies; but although 

 these were his favourite studies, his acquaintance with general 

 chemistry is proved by his ' Elements of Experimental Chemistry,' 

 to have been both sound and extensive. This work was one of the 

 first on chemical science published in this country, which combined 

 great literary elegance with the highest standard of scientific accu- 

 racy. His comparative analysis of many varieties of British and 

 foreign salts were models of accurate analysis, and were important 

 in dispelling the prejudices then popular in favour of the latter for 

 economical purposes. His ' Memoir on the Theories of Galvanic 

 Decomposition' earned the cordial approval of Berzelius, as being 



