Bio^rrapfiical Memoir of the late Dr Henry. 13 



numbers of atoms existing in equal spaces of aeriform mat- 

 ter, has almost elevated the pneumatic chemistry to the dignity 

 and exactitude of a mathematical science. There is, moreover, 

 in the pursuit of these subtle elements, which escape the visual 

 sense, which can be imprisoned and weighed only by the most 

 refined instruments, and which can be discriminated only by 

 the most delicate processes and indications, a somewhat of mys- 

 tery and of a higher initiation, which deeply moves the imagi- 

 nation. It may too be safely affirmed, that Dr Henry's habits 

 of extreme mental accuracy, his unrivalled manual expertness, 

 and the general tendencies of his tastes towards elegance and 

 precision, peculiarly qualified him to excel in conducting such 

 delicate enquiries. 



But although his original efforts in chemistry were mainly 

 directed to the gases, he was by no means a stranger to other 

 provinces of experimental research. His comparative analysis 

 of many varieties of British and Foreign salt, were important 

 in refuting the prejudices, then widely prevalent, of the supe- 

 riority of the latter for certain economical purposes. His essay 

 on the Materiality of Heat, published in the memoirs of this 

 learned body, is written with force and perspicuity, though in 

 modern times the tide of doctrine undoubtedly sets in the oppo- 

 site direction. His critical memoir on the theories of galvanic 

 decomposition has even lately been noticed with praise by Ber- 

 zelius in his Jahrsbericht, as among the first to assert that view, 

 which in his juilgment is still most deserving of adoption. But 

 of the soundness and extent of Dr Henry's acquaintance with 

 general chemistry, his "Elements" furnish undoubted proof. 

 This work, which in 1829 had passed through eleven editions, 

 has always held a high place in public estimation, as a clear and 

 faithful record of the details of chemistry, and as conveying, in 

 its general chapters, a distinct and comprehensive survey of the 

 leading doctrines and higher philosophy of the science. 



Although impelled by a strong predilection to the pursuit of 

 chemical science, Dr Henry was not an inactive member of the 

 profession to which he belonged. Besides contributing to the 

 medical journals of the time, such interesting cases of disease as 

 fell under his observation, as physician to the Mancliestcr In- 

 firmary and other public charities, he engaged in an elaborate 



