580 Dr. A. C. Orehore on an Atomic Model 



oriented with respect to each other on the supposition that 

 all directions are equally probable, it has been shown * 

 that the average value of this quantity is 2/3. The process 

 of averaging the square of this quantity is here omitted, 

 because it is not essential that the coefficient of ft 4 be known 

 for our purposes. The average, however, comes out 22/45. 

 Hence the average force upon the first ring due to the 

 second for all orientations is 



F _ EiE 2 (l-fe 2 ) / _ \ 



(61) 



This result includes all orders of ft up to ft and merely the 

 inverse square of the distance. Expanding (1 — y^i 2 ) - * in 

 series, and multiplying by (1— ft 2 ) gives 



l+W-zW+fft'-i/S, 



W 



Multiplying this into the last parenthesis of (61) gives the 

 complete result, including terms in ft, as 



. . . (62) 



IV. 



Comparison between the Results obtained using the Larmor- 

 Lorentz and the Saha Forms of the Fonderomotive Force. 



The average force between two point charges revolving in 

 circular orbits resolved along the centre line according to 

 the Larmor-Lorentz theory has been obtained f as follows : — 



(i + W+W + W ■■•■)■ ■ ( 63 > 



The velocity of the first point charge, upon which this 

 expresses the force, does not appear at all in the expression. 

 According to the result in (61) this statement would also 

 have been true in the Saha investigation, were it not for 

 the presence of the factor in the coefficient, (1 — ft 2 ) - *. 

 This factor may be traced back to the original expres- 

 sion (3). This difference is fundamental, and has con- 

 siderable significance. Suppose, for example, the force 

 upon a first moving point charge due to a second charge 



* Phys. Rev. July 19] 8. p. 20. 



t Phys. Rev. Feb. 1919, p. 91, eq. (4). 



F= _E i E ; 



