MODELS OF POSITIVE ION 327 



that it cannot communicate its energy to the 

 aether- -assuming that the aether has a molecular 

 structure of great density, which is probably the case. 



In such circumstances the energy of the elec- 

 tron will remain stored up in the part of the 

 aether occupied by the atom and an envelope 

 surrounding it. 



At a collision, when another atom or molecule 

 comes within the region of the envelope it will be 

 We may write 



«-.^-ra-(")'^K?)* ] 



ABC 



••^ = ^i + x-^ + xi + re- 



If a is small compared to A, all terms higher than the first 

 must be negligible. 



Sin • -T- is small; so that \ is never equal to / — ,but 



must be a small fraction of this. Therefore it is only when X 

 is large compared with a that a wave is freely propagated. 

 If we write cos {wt - Ex) in the form 



27r /t x\ 



A 



But the very highest value of u requires that 

 Ka TT , 

 -2=2' ^^''"^ 



TT 27r 



- = —- or X = 2a. 

 a A. 



Now for a wave in a uniform wire of the same tension 



< 





- 25r 27rr 



and to = — = — -— . 



r A. 



Hence A >■ ira. 



