

182 RADIATION FROM ELECTRONS [CH. xix. 



speed of light, two electrons at opposite ends of a 

 diameter radiate about one-tenth as much as either 

 alone ; four electrons at the corners of a square, 

 likewise rotating with one -tenth of the velocity of 

 light in its own plane, will have a radiating power 

 of about one six-thousandth of that of one of them. 

 But if the velocity of the particles is only one- 

 hundredth that of light as must often, perhaps 

 usually, be the case among constituent electrons 

 in an atom, then a pair would radiate only 

 one-thousandth as much as one. For three, the 

 radiating power is diminished to about one two- 

 millionth ; and for six, to something getting on 

 for a trillionth, which practically means no radiat- 

 ing power at all. 



The actual numbers, and the calculation, can be 

 found in the Philosophical Magazine for December 

 1903, p. 681. 



All this depends on the electrons being sym- 

 metrically situated round the centre of rotation ; 

 but if by any cause such as an atomic clash or 

 chemical collision they are displaced from sym- 

 metry, then their centre of gravity will rotate 

 round the original centre, and will act as a single 

 electron, or rather as an electron of multiple mass 

 and constitution. The constituent particles will now 

 not compensate each other at all, so far as this 

 excentric motion is concerned. Accordingly the 

 , y radiation instantly becomes violent, and must be 

 regarded as the source of the visible spectrum: the 

 nature of the lines depending on the structure of 

 the composite body, which, by reason of temporary 

 displacement, now acts as a single radiator of great 

 power. In this way it is possible to conceive of the 

 particular kind of radiation, exhibited in the spectrum, 



