( 351 ) 



Operaring agaia with expressions that contain the factor «'"', we 

 can satisfy (1Ü) and (11) bv the values 



P2 = -\- i Pl , I'. z= 11-2 -j- n^' , 



and likewise bv 



/)j = — i pi , n =: /i; — «-.' , 



the change in the frequency being given by 



, _ fe _ ^ ^ _ ^^ 

 3 ji, 6 o 6 m ' 



III both eases we have to do with a combination of a Yxy- and 

 a I'xY -vibration, the two vibrations having equal amplitudes, and 

 differing in phase by ^/^ period. 



From- (12) and (13) we deduce the possibility of two similar 

 combinations of a i'xc- and a i.,-vibration ; the frequency is 



for one combination, and 



for the other. 



§ 10. Similar results are obtained by supposing that a charge 

 is distributed with uniform volume-density o over a spherical space 

 and that each element of volume, after having undergone a dis- 

 jilaeement a from its position of equilibrium, is acted on by an 

 elastic force, proportional to the displacement. Let kr a be this force 

 per unit volume, (t the uniform volume-density of the ponderable 

 matter, and let us suppose that this density is invariable and that, 

 besides the charge 0, the sphere contains an equal charge of opposite 

 sign that is iminoaible. Then, outside the magnetic field, a motion 

 reproseuted by 



(U) 



may take place. 



By / I have now indicated the direction in space in which the 

 solid harmonic H^t increases most rapidly, and the differential coefl&- 

 cient is to be understood as a vector in that direction. The factor n 

 is still ot the form (2), and lor the frequency I find 



