Chase.] 



24 



lApril 16, 



the terrestrial movements are either independent of the absolute tempera- 

 ture, or standing in unknown relations to it, the simplest evidence of 

 equivalent vis viva should be sought at some specific temperature, and in 

 the most typical and most widely diffused gases. We have already seen 

 that the universal typical liquid, H.^0, furnishes data for a ready determi- 

 nation of Joule's equivalent, at the mean temperature of solidification 

 (3°C = 35°. 6 F); let us examine the constituent typical gases (H,0) at the 

 same temperature. 

 According to Clausius,* the mean velocities of the molecules are : 



Oxygen, 

 Hydrogen, 



At 0°C. 

 461 m = 1514 ft. 

 1844 m = 6050 ft. 



At 2°C. 

 464.4 m = 1535.1 ft. 

 1857.5 m = 6094.8 ft. 



Earth's equatorial velocity of rotation (1535.78 ft.) accords with the 

 molecular velocity of oxygen ; its velocity of revolution is 16 times the 

 veh)cily of hydrogen, l^io^ represents the atomic weight of any perfect 

 gas n, the velocity at 3°C may be found by the equation : 



l/ Wj 



16 





The mean molecular velocity of ox/gen and hydrogen (3048.7), is to 

 Eartli's orbital velocity, as the square of the time of fall to the ceutre from 

 any distance d, is to the square of the time of orbital revolution at d. 



The following comparison with the results of Cornu's and Michelson's 

 experimental determinations of the velocity of light, and with my own 

 estimation of Sun's mass and distance from the explosive energy of Hp,f 

 will show the closeness of agreement between the chemical and other 

 physical approximations. 



It may be interesting, in this connection, to give two additional illustra- 

 trations of the tendency to harmonic wave lengths in elementary spectra, 

 of which I have already presented many evidences.:}: 

 ■ If we take n = ^is, we find that Vogel's wave-lengths, g of the ultra- 

 violet lines in the spectrum of hydrogen, are strictly harmonic, as will be 



* Phil. Mag., 1857, xiv, 124. 



t Proc. Am. Phil. Soc, 1872, xii, 394. 



JProc. Am. Phil. Soc, xvii. 109-12, 295-301 ; xviii, 224-6. 



§ Photographic News, February 20, 1880. 



