2G2 Prof. TV. Peddie on the 



will be feeble in comparison with tbat associated with the 

 lines. But it is possible to have an atomic structure in 

 which the line emission is produced by the revolution of the 

 electrons in the interior of the atom, and not by their linear 

 vibrations about fixed positions. In the preceding case the 

 trouble is that, as radiation proceeds, the kinetic energy of 

 the electron diminishes, and the electron gradually sinks in, 

 with exhaustion of potential energy, to the region of in- 

 finitely slow revolution. In so far as this action is concerned, 

 the spectrum of a glowing gas would be continuous. The 

 trouble was avoided by banishment of the continuous part 

 to a non-experimental range. There is only one way of 

 practically avoiding it (see, however, § 5). 



The energy of the radiation must be drawn from an internal 

 store in the atom, the magnitude of which is very large in 

 comparison with the circulatory energy of the electron itself. 

 The positive electricity in the shell within which the electron 

 circulates stably must itself be in rotation, and, if necessary, 

 drag the electron with it. Thus the period of the circular 

 vibration acquired is to some extent independent of the 

 tangential component of the speed of an electron entering 

 the atom from without. If v n is the period associated with 

 one of the shells, the condition for steady revolution of the 

 electron is 



±Tr~mv n Xp^ p n ~J 



Hence the attraction within the shell is proportional to the 

 distance from the centre. At the surface r — r n \ a uniform 

 surface distribution of positive electricity must be located, 

 its amount being that requisite to raise the total charge 

 within to the value 



- 7rp n r n % 



where 



4 ??i n „/l IV 



6 e \p x 2 p n * y 



At the surface r—r n ", a uniform negative distribution 

 must be placed, its amount being that required to make the 

 force become a repulsion F : (r»"): and so on. The shell of 

 positive electricity within the range r n " —r n ! rotates round 

 a central axis with angular velocity 



in which the surface distributions may share. 



