150 BIOGRAPHICAL MEMOIR OF JOSEPH HEXRY. 



how truth was won and knowledge advanced in one fiekl of inquiry, 

 they would gain the aptitude which any real investigation may give, and 

 the confidence that springs from a clear view and a sure grasp of any 

 one subject. 



He understood, as few do, the importance of analogy and hypothesis 

 in science. Premising that hyi:)othesis should always be founded on 

 real analogies and used interrogatively, he commended it as the pre- 

 requisite to experiment, and the instrument by which, in the hands of 

 sound philosophers, most discoveries have been made. This free use of 

 hypothesis as the servant and avant-courier of research — as means rather 

 tlian end — is a characteristic of Heivey. His ideas on the subject are 

 somewhat fully and characteristically expounded by himself in his last 

 presidential address to the Philosophical Society of Washington — one 

 which he evidently felt would be the last. 



How Henry was valued, honored, revered at Princeton, the memo- 

 rial i)ublished by his former associates there feelingly declares. AVhat 

 he did there for science in those fourteen years would be long to tell 

 and difficult to make clear without entering into details, here out of 

 place. Happily the work has been done to our hand by the Professor 

 himself, several years ago, in a communication which is printed in the 

 index volume of the Princeton Eeview, and reprinted in the Princeton 

 Memorial. This careful and conscientious, though cursory, analysis of 

 the principal researches of that period we propose to append to this 

 record.* There is also in preparation, by a competent scientific hand, a 

 detailed list of all Professor Henri"'s contributions to science, which we 

 desire likewise to appeud.f , 



One of these, of the Princeton period, ought to be mentioned. It is 

 upon the origin of mechanical power and its relations to vital force. It 

 is a characteristic example of Professor Henry^'s, happy mode of treat- 

 ing a scientific topic in an untechuical way. It also illustrates his habit 

 of simply announcing original ideas without putting them prominently 

 forward in publication, as any one who was thinking of himself and of 

 his own fame would be sure to do. The doctrine he announced was com- 

 municated to the American Philosophical Society in 1844 in brief out- 

 lines. He developed it further in an article published in the Patent 

 Office Eeport for 1856, twelve years later ; a medium of publication which 

 was naturally overlooked. Only at a friend's desire was the paper re- 



* See Suiiplemeutary Note II. A Letter from Professor Henry. 



t See Supplementary Note III. A List of Professor Henry's Scientific Papers 



