ADDRESS OF PROF. W. B. ROGERS. 87 



former of these qualifications we have proof in the readiness with 

 which he could devise means, at once simple and efficient, for 

 his investigations, such as are seen in the construction of his 

 first electro-magnetic machine, in the conversion of the electro- 

 magnet into a means of signaling at a distance, in the thermal 

 telescope by which he noted the heat reflected from clouds or distant 

 objects on the land, in his device for measuring the velocity of 

 projectiles, and in that by which he measured the tenacity of liquid 

 films of differing curvature, anticipating PLATEAU'S later and 

 fuller researches, and in numerous other instances which we may 

 not here recount. 



Of his clearness and comprehensiveness in the discussion of 

 scientific questions perhaps no better example can be cited than the 

 remarkable paper on the "Origin of mechanical power and the 

 nature of vital force," which, following at a very short interval the 

 publications of GROVE, MAYER, and JOULE on the conservation 

 of forces, for the first time clearly expounded and illustrated the 

 application of this the grandest of the generalizations of modern 

 science to the organic world. 



Ingenious, zealous, and patient in experiment, HENRY was most 

 conscientious in reporting his results, allowing no preconceived 

 theories to modify the record or to warp the conclusions to which it 

 pointed. He loved scientific truth supremely, and the discovery of 

 it was a source of unalloyed delight, for he had early been a greedy 

 .seeker of knowledge, and had learned, as Lord BACON has said, 

 that "while in all other pleasures there is satiety, of knowledge 

 there is no satiety, but satisfaction and appetite are perpetually 

 interchangeable." 



As in the case of most men who have attained eminence in science, 

 HENRY used his imagination as a stimulus and even as a guide to 

 his investigations ; but while in the course of his work he could 

 not but frame hypotheses, he treated them as but the scaffolding to 



