1904.] Ions ly Electromagnetic Disturbances, etc. 



which is exactly restored during the remaining portion. If, however, 

 we take account of radiation from the ion, this will no longer be the 

 case. Energy will be definitely abstracted from the pulses and radiated 

 away from the ion. In this case the passage of a complete pulse no 

 longer restores the original velocities unless the energy absorbed by 

 the ions is radiated away before the pulse has passed. This will not, in 

 general, be the case. Hence, even if radiation be taken into account, 

 there must still be a drifting of the ions. Indeed, the general effect of 

 the radiation will be to give the ions real velocities instead of what I 

 have called apparent velocities. 



These results seem to me to have an important bearing on the theory 

 of Rontgen rays and of the action of radio-active substances. We may 

 regard a radio-active substance as the origin of electro-magnetic 

 disturbances radiated outwards. These may ionise the gas in the 

 immediate vicinity of the substance, and we shall then have a streaming 

 of positive and negative ions and probably also of neutral molecules, 

 both outwards from the substance and inwards to it. This view is 

 quite in agreement with the apparently material character of part of 

 the radiations (indeed it would explain it), but it does not require the 

 supposition that there is a continual diminution of the radio-active 

 substance. 



The question arises whether the velocities set up in the ions are of 

 the order that experiment indicates. If the impulses radiated are set 

 up by collisions of ions in the active substance, it appears to me that at 

 least in the immediate* vicinity of the substance, the velocities set up 

 may be comparable with the velocities of the ions which produced the 

 impulses. 



The velocity of the material particles in the radiations from active 

 substances are comparable with V. It will thus be seen that the theory 

 suggested here requires that wd should be comparable with Y. Now 

 w is the angular velocity with which the ion described the circular 

 path in passing through the pulse, and is thus the measure of the 

 frequency of the vibrations set up in the ion. If d is of the order of a 

 wave length of visible or ultra-violet light, then <o must be of the order 

 of the frequency of visible or ultra-violet vibrations. Hence the 

 theory requires that associated with the impulses we should have 

 visible or ultra-violet light. I think it must be admitted that this 

 is in harmony with the experimental evidence on ionising agents 

 generally. Per contra we may argue that if any system is an origin 

 from which electro-magnetic pulses of great intensity are radiated, we 

 shall have associated with these, in its immediate vicinity, streams of 

 ions moving with great velocities, and trains of waves which may be of 

 such frequency as to come within the visible spectrum. Thus the 

 distinction between bodies turns on the character of the impulses, and 

 is a difference of degree rather than of kind. 



