based upon Electromagnetic Theory. 581 



at rest — that is. having zero velocity and acceleration — is com- 

 pared. The Larmor-Lorentz equation for the instantaneous 



E E 

 force reduces to the electrostatic force. F = ~~"R, which 



means that it is immaterial whether the first electron is 

 in motion or not. The Saha instantaneous force by (3) 

 becomes 



R 8 (l-£ 1 , > 



R, (64> 





which makes the force depend upon the state of motion of 

 the first charge. This result seems to the writer more 

 rational than the former, for it is difficult to believe that 

 differing physical states should find no expression in the 

 force, as in the former result. 



There is another difference that makes it almost conclu- 

 sive that the Larmor-Lorentz equation does not represent the 

 true force, while the Saha force may. There is an accelera- 

 tion term in the former equation, 



which at great distances gives a force that varies inversely 

 as the distance R. The two R\s in the numerator cancel 

 two of the three in the denominator, leaving the term 

 varying as the inverse distance. At great distances the 

 inverse distance term is in excess of any term varying as 

 the inverse square or higher orders, and represents the 

 whole force. The direction of the force is immaterial. No 

 such law of force is known in experience between systems 

 at a great distance, and it taxes the imagination to believe 

 that this represents the truth in the case of two charges. 



On the other hand, the Saha equation (3) gives no term 

 varying as the inverse distance, the lowest order being,' the 

 inverse square, which is entirely in accord with experience. 

 There is no acceleration term in the Saha expression. 



V. 



Application to Two Material Bodies composed of 

 Neutral Atoms. 



If an equation like (63), resulting from the Larmor- 

 Lorentz theory, is applied to two neutral bodies composed 

 of atoms each having certain charges in rotation and an 

 equal number of stationary charges of the opposite sign, it 



