William Henry. 125 



to the Royal Society a proof of his activity, if not of ac- 

 curacy, in his inquiry if carbon was an element, and in 

 1800 in his experiments on muriatic acid. He had ob- 

 tained a facility of operating on gases, and by the electric 

 spark decomposed that acid over mercury, obtaining calomel 

 and hydrogen, or without the mercury, that which was in 

 time called chlorine. It was, however, left to another to 

 explain these results. In 1803, he- showed the effect of 

 pressure on the absorption of gas by water, supporting the 

 theory of Dalton that it was due to mechanical agencies. 



We may say that his care and his refinement contri- 

 buted very much to the knowledge of the analysis of gaseous 

 mixtures and compounds, and we especially owe to him 

 the knowledge of the composition of coal gas and various 

 methods of ascertaining it. His method of using chlorine 

 was long employed, although bromine, &c., have now taken 

 its place, and he applied also spongy platinum in a manner 

 which for a while was considered the most convenient way 

 of uniting oxygen with hydrogen and with carbonic oxide 

 when at 340 Fahr. 



Dr. Henry's large work, a system of chemistry, had 

 passed through eleven editions in 1809, and may still be 

 consulted with advantage by those who wish to learn the 

 history of the best method of operating with eudiometers. 

 Although not strong, he both studied the science to which 

 his father had introduced him, and practised medicine, 

 whilst his active mind could not refuse to write papers on 

 that subject also, and his general love of knowledge com- 

 pelled him to attend somewhat to the progress of every 

 other department of scientific inquiry. We may consider 

 him as taking the place of Dr. Percival on the demise of 

 that gentleman ; he had the same refinement of manner, 



