CHAPTER V. 



DETERMINATION OF SPEED AND ELECTROCHEMICAL 

 EQUIVALENT OF CATHODE RAYS. 



IF the cathode rays consist of flying electrified 

 particles they will be deflected, or their paths curved, 

 by the proximity of a magnet : and this is a well 

 known and prominent fact concerning them. With 

 some care the amount of deflexion, caused by a 

 magnetic field of known strength, may be measured. 



The curvature of path produced in cathode rays 

 by a transverse magnetic field, or, the amount of 

 spirality produced by a longitudinal magnetic field, 

 constitutes an evident mode of attacking the problem 

 of estimating their velocity. 



If the velocity is constant and the magnetic field 

 uniform, the curve into which the stream is bent 

 round the lines of force will manifestly be a 

 circle ; and its course can be readily traced either 

 directly, after Crookes' manner, by letting it graze 

 a phosphorescent substance, or indirectly by inference 

 from the position of a linear target placed so as to 

 catch the deflected, rays. If the direction of velocity 

 is inclined to the direction of the field, the course of 

 a particle will be compounded of a circular motion 

 round a line of force, and an unchanged rectilinear 

 motion along it : that is to say, it will be a spiral,. 



