DISCOURSE BY REV. S. B. DOD. 143 



who love speculation rather than study. He never took anything 

 for granted, never despised the details of his work, but carefully 

 established, step by step, those data on which he based his con- 

 clusions. In 1849 he says, " Since my removal to Princeton I have 

 made several thousand original investigations on electricity, mag- 

 netism, and electro-magnetism, bearing on practical applications of 

 electricity, brief minutes of which fill several hundred folio pages. 

 They have cost me years of labor and much expense." 



Combined with this thoroughness, there was great fertility of 

 mind. He was distinguished not in one branch of physics, but in 

 all. In the catalogue of his published papers (and these represent 

 but a small part of his work, for he worked much and published 

 comparatively little) there is evidence of the varied fields in which 

 he wrought. While a large part of them are devoted to his favorite 

 and most famous line of research, yet there are numbers of them on 

 problems in acoustics, on acoustics applied to building, on building 

 materials, on the sun spots, on natural history, on the prediction 

 of the changes in the weather, on various problems in meteorology, 

 on capillarity, on light and heat, on the velocity of projectiles, on 

 the correlation of forces, and the conservation of energy. 



He was possessed of great foresight. The various forms of electro- 

 motors which have since been attempted are all on the basis of Pro- 

 fessor HENRY'S made thirty years ago ; nor has all the ingenuity 

 and money expended since that time advanced us one step beyond 

 the conclusion which he reached then. " I never regarded it as 

 practical in the arts because of its great expense of power, except 

 in particular cases where expense of power is of little consequence." 



The results of his labors I can only briefly sum up. 



As president of the American Association for the Advancement 

 of Science, and of the National Academy of Sciences, he gave the 

 weight of his influence and the benefit of his experience to the suc- 

 cessful conduct of these societies. 



He was Chairman of the Light-House Board, and during the 

 rebellion, a member of the commission to examine inventions for 

 facilitating military and naval operations. 



In these varied capacities he has served the Government with 

 zeal and fidelity, and has made his scientific knowledge of avail in 



