148 The Smithsonian Institution 



tion of fuel). 1 It would therefore appear to follow that animal 

 power is referable to the same sources as that from the com- 

 bustion of fuels [namely, the decomposing energy of the sun's 

 rays]. . . . Vitality is that mysterious principle which propa- 

 gates a form and arranges the atoms of organizable matter, 

 while the power with which it operates, is derived from the 

 divellent power of the sunbeam." 1 



Later, in 1857, his theory was more fully elaborated, and 

 even then long antedated Doctor William B. Carpenter's bet- 

 ter known essay, " On the Application of the Principle of the 

 Conservation of Force to Physiology," 1884, in which much 

 of the same ground was gone over as if for the first time, 

 the author being evidently in ignorance of Henry's previous 

 paper. Others had, however, been at work between 1844 

 and 1857, and it was to this fact that Professor Levering 

 alluded when he said : 



" In this connection Henry's views on the correlation of 

 the physical and organic forces may be recalled, which only 

 lacked the fuller development and wider publication which he 

 finally gave to them to have secured for him the first com- 

 plete announcement of one of the grandest generalizations of 

 modern science." 8 



The latest and most comprehensive generalization in phy- 

 sics that which culminated in the researches of Hertz 

 seems also in a certain way to have been foreseen by Joseph 

 Henry, much as those of Joule were foreseen by Lord Bacon 

 and by Thompson. 



" Faraday's immortal researches, Clerk Maxwell's pro- 

 phetic investigations, and Hertz's convincing experiments," 



1 This condensation is Henry's own, and is 2 Scientific Writings of Joseph Henry," 



contained in Professor Taylor's " Memorial Volume I, page 222. 

 of Joseph Henry," page 273. 3 Memorial of Joseph Henry," page 438. 



