Astronomy and Electrical Theory of Matter. 517 



On the other hand, if the spring factors about CD, AB 

 are R" 1 , S _1 , the potential energy of the system is given by 



2U = R- 1 c/) 2 + S- 1 ^ 2 . , 



Now let <9 = 90°-/3, £=#, ^=-*/, 



and C=L, B = N-L(L<N), Csin/3 = M, 



so that 7 2 = Csin 2 /3/(B + C). 



Then the kinetic and potential energies are the same in the 

 two problems, and an exact analogy is established. The 

 charges are represented by the angular displacements of 

 the sphere and the ring. 



The defects of this mechauism are the absence of sym- 

 metry and the fact that the coupling cannot be carried to 1 

 unless L-N, B = 0. Prof. Barton desires a mass M to 

 represent the mutual induction. This seems to be a mistake. 

 The coupling in the electrical system is introduced not by 

 making any addition but by changing the configuration 

 of the parts. This feature is particularly well illustrated 

 by the effect of altering the angle /3 in the mechanism 

 described. 



Dunsink Observatory, 

 Oct. 27, 1917. 



XLIX. Astronomical Consequences of the Electrical Theory 

 of Matter. Supplementary Note by Sir Oliver Lodge *. 



IT is barely possible to expound the position more clearly 

 than Professor Eddington has expounded it in two 

 admirable papers which have appeared in the September and 

 October issues of the Phil. Mag.; but a summary may be 

 convenient. 



It is so unusual to take account of varying mass that 

 traps lie in wait for the unwary, and one is apt to overlook 

 some of the consequences, or to deal with the variations 

 incompletely. 



When thoroughly considered, a force which increases speed 

 is opposed by an inertia different from that encountered by a 

 transverse or merely deflecting force, for the longitudinal 

 or tangential force contains the term vdm/dt as well as the 

 term mdv/dt. 



It is better therefore to deal with momentum throughout, 

 and so avoid the complication of a difference between longi- 

 tudinal inertia and transverse inertia. (See Note 2.) 



* Communicated by the Author. 



