imK] ^^'J [Cbi.se. 



original sources and maxima of deposits— sliortening the 

 radii of areas of violent variations, and even of noncon- 

 formability — and embarrassing the best laid plans for 

 restoring the state of things in ancient days. 



Photodi/namifx. By Pliiii/ Earle Chase, LL.D. 

 {Read before the American Philosophical Society, Jan. 7, 1881.) 



Tlie general laws of motion have been largely studied in connection 

 with the special departments of Thermodynamics and Electrodynamics. 

 Little attention lias been paid, comparatively speaking, to the much 

 broader field of Photodynamics. 



Sir John Herschel showed* that the elastic force of the air, in its resist- 

 ance to compression, would require to be increased, " in proportion to the 

 inertia of its )nolecules," more than 1,000,000,000,000 fold to admit of the 

 propagation of a wave with the velocity of light, and that this enormous 

 physical force is perpetually exerted at every point, through all the immen- 

 sity of space. He also saidf : "It must be remembered that it is Light, 

 and the free communication of it from the remotest reyion of the universe, 

 which alone can give and does give us the assurance of a uniform and all 

 pervading energy." We have no equally positive evidence of the direct 

 transmission of heat and electricity from the heavenly bodies, and inas- 

 much as all thermal and electrical phenomena can be explained by local 

 transformations of simple radiant energy, the philosophical basis of Pho^ 

 todynamics appears to be better grounded than that of either Thermodj'- 

 namics or Electrodynamics. 



In 1863, I began a series of general kinetic investigations, in confirma- 

 tion of views which maybe expressed by the following general postulate : 

 All physical phenomena are due to an Omnipresent Power, acting in ways 

 icMch may be represented by harmonic or cyclical undulations in an elastic 

 niedium. In my first paper:}; I showed the importance of tlie fundamental 



equations v =^ ~; /i = '- ^= the modulus of o ; in which t represents the 

 /J 4 



time of cosmical, molecular, or atomic rotation, and // represents the ac- 

 celeration of a central force. 



By combining these equations with considerations deri\ed from the 

 equality of elastic actions and reactions proportioned to mass, and from 

 tendencies to conservation of areas, I found that the daily and annual fluc- 

 tuations of the barometer furnisli harmonic indications of Sun's mass and 

 distance, and I announced my confident expectation of other astronomical 



* Familiar I,ectnre.s on Scientific Subjects, pp. 281-3 



+ Ib. p. 218. 



tProc. Am. Phil. Soc, vol. i.x, pp. 28o-S. 



