998 Dr. Dorothy Wrinch on the 



doublet. If it is projected towards the doublet, it goes to 

 the point r = r 2 and then recedes to infinity ; otherwise 

 it moves away from it at once. 



We have therefore two different types of motion, which 

 are typical of the asymmetry of the field of force of the 

 doublet. If the particle is in the line = 7r, so long as 

 .he angular velocity is zero, no conditions of projection can 

 prevent the particle from receding from the doublet with 

 increasing speed, either immediately or after an interval 



' 2r 2 \/r l 2 — r 2 2 / \/2fi. 



If, however, the particle is in the line = 0, so long- 

 as the angular velocity is zero, the particle does not leave 

 the system unless projection is away from the origin and the 

 velocity attains or exceeds the critical value \/2/j, / r.^. 

 If the velocity of projection away from the origin is less 

 than V2fjb/r 1 — and this includes the case of zero velocity 

 or of projection towards the centre — the particle approaches 

 the centre after an interval 



2r 2 \/r 2 2 — r* I */ifi, 

 or directly, according as U 1 >0 or Ui < 0, r 2 being given by 



and the particle arrives at the centre in a finite time with 

 infinite velocity. 



These conclusions lead to curious effects of electrical 

 doublets in the presence of stray electrons, which have 

 apparently not been completely realized. It is remarkable 

 that these stray electrons, when placed on one half of the 

 axis of the doublet, should arrive from any distance, however 

 large or small, and bombard the doublet with very great 

 momentum ; and that, on the other hand, they must leave 

 the system altogether if they are on the other side of the 

 axis. It follows that a necessary consequence of the field 

 of force created by a doublet is a continuous bombardment 

 on one side by any stray electrons, and a steady ejection 

 of electrons from the system on the other side. 



General Motions. 



Thus far, we have considered only the case when particles 

 are projected from some point on the axes of symmetry 

 of the doublet, with no angular velocity. The angular 



