1885.1 ^* ' [Chase. 



Thermo-electro-photo-baric Unit. By Pliny Earle Chase, LL.D. 

 (Read before the American Philosophical Society, April 17, 1885.) 



The earliest attempt at measurement, "with a view to demonstrate the 

 correlation of thermal and electric energies, appears to have been that of 

 Principal Forbes, who found, in 1832 (P. Mag., iv, 27), that the conduc- 

 tivity of metals for heat and electricity, is nearly the same. The dimen- 

 sions of absolute measure involved were M, L. 



In 1843, Joule published his discussion of the calorific effects of mag- 

 neto-electricity, and his determination of the mechanical equivalent of 

 heat {P. Mag., xxiii, 263, 347, 435), using the same dimensions, M, L. 



In 1856, Weber extended the correlation of Forbes (Pogg. Ann., xcix), 

 by showing the approximate equality of the electro-magnetic ratio to the 

 velocity of light (L T-^). 



Wolf's discovery of the sun-spot period was followed, in 1857, by the 

 investigations of Lamont and Sabine, showing the identity of the sun-spot 

 periods with the periods of magnetic perturbation {ATag. and Meteor ol. Obs., 

 Toronto, III, Ixviii ; St. Helena, II, cxxi-cxxxvi). 



In 1860, Henshall showed the influence upon sun-spots which is pro- 

 duced by Mercury, Venus and Jupiter, when in conjunction with the 

 same face of the Sun {Cosmos, xvii, 573). 



In 1863, Chase showed {Proc. Amer. Phil. Soc, ix, 283-8; P. Mag., 

 xxviii, 55-9) that the mass of the Sun can be approximately estimated 

 from the influence upon the barometer of the constrained "relative mo- 

 tions" of the Earth and Sun. In 1864, he showed, by the investigation 

 which received the Magellanic medal {Trans. Amer. Phil. Soc, xiii, 117- 

 36 ; Proc. Amer. Phil. Soc, ix, 425-40 ; P. Mag., xxx, 52-7), that the mag- 

 netic disturbances of the Sun and Moon are many times greater than 

 simple tidal disturbances, and that they can be very closely represented 

 by the disturbances of gravitating pressure, under constrained and " coerci- 

 tive" relative motion. In 1869, he further showed (Proc. Amer. Phil. Soc, 

 xi, 103-7), that the constrained relative motion at Sun's surface represents 

 a cyclical gravitating and electric disturbance which acts with the velocity 

 of light. 



In 1873, Maxwell (Electricity and 3fagnetism), published his theory 

 that light consists of a disturbance in a medium susceptible of dielectric 

 polarization. 



In 1884, Langley (Researches on Solar Heat), confirmed the identity of 

 thermal, electric, and luminous radiation, for which Chase had suggested 

 probable reasons in 1864 (Proc. Am. Ph. Soc, ix, 408), and Draper in 

 1872 (P. Mag., xlvi, 104-17). 



All of the foregoing investigations can be coordinated, in the region of 



greatest known energy, by means of the kinetic unit g — > ^^ "which /j. rep- 

 resents an infinitesimal particle, and v^ is the velocity of light, the elec- 



PROC. AMER. PHILOS. SOC. XXII. 120. 2v. PRINTED JULY 24, 1885- 



