784 Sir Oliver Lodge on the Transmission 



Hence, denoting the quantity — — 5_ by u, and the maximum 



or ultimate value of -=-, apart from oscillations, by w, we 

 have the equation 



v 2 — (v—w) 2 = u 2 ; 

 -or, since u is generally decidedly smaller than i\ 



u 2 e 2 LLm 2 \ 2 



2v~ 16 



7r 2 m 2 v 



The particle will be joggled forward with twice this speed 

 every time a ventral segment reaches it, and will be reduced 

 to momentary rest in the suck- back of the nodes. 



On showing this to Professor Poynting he stated his belief 

 that a resistance term had been omitted from the original 

 equations, a term expressive of the energy consumed in 

 radiation whenever a charge is accelerated. Indeed a moving 

 charge seems likely to be in a curiously unstable condition, 

 for although it encounters no resistance as long as its velocity 

 is uniform, yet directly there is acceleration of any kind, 

 -even retardation, it must begin to transfer its energy to the 

 ether in a way which is equivalent to the action of a retard- 

 ing force ; so that an initial retardation would tend to be 

 intensified, and thus apparently an electron could be readily 

 induced to stop dead. If this be the case, then the opacity 

 hereafter treated may depend not merely on the newly born 

 ions, as hereafter supposed, but on the total ionic, or at least 

 electronic, content : and the sweeping up of the ions would 

 itself constantly make a call upon the energy of the pro- 

 pelling waves, unless their motion could be guaranteed 

 absolutely uniform. I do not propose to attempt to develop 

 this important suggestion, and will proceed without further 

 reference to it. 



The inverse electrochemical equivalent e/m is 10 7 /\// / ' c -£- s * 

 units, and the wave-energy per c.c. is yu,H 2 /87r ; (remembering 

 the electric energy as well as the magnetic, and also the fact 

 that H is the maximum, not the average, of H). 



c ae 2 uH 2 X 2 



So w=^2-. ^ — -^ — ; 



111" 07T J.7TV 



and the velocity imparted to the particles is proportional 

 both to the energy-density and to the square of the wave- 

 length. Short waves, like those of light, cannot be expected 

 to do much in the way of propulsion, except perhaps in the 

 neighbourhood of the sun where they are very intense ; but 

 anything like radiation of Hertzian wave-length may be 



