July 20, 1900.] 



SCIENCE. 



101 



regarded as the most reliable. And yet 

 these are the raethods whose results differ 

 most widely. 

 As the difference appears too great to be 



and velocity. But in the method of Kauf- 

 mann and Simon it is assumed that the 

 whole potential energy of the corpuscle 

 when at the surface of the kathode is trans- 



Values of ejm FOE Kathode Rays. 

 (The results are expressed in c. g. s. electromagnetic units.) 



Velocity. 

 [Velocity of Light = 1]. 



ejm -=- 10« 



I. Magnetic deflection and kathode potential. 



II. Magnetic deflection and velocity of rays. 

 Hev = V determined by the method of Des Condres. 



Wiechert. 

 Wiechert. 



1897 

 1899 



Hydrogen. 



0.1 

 0.132 — 0.167 



[20 — 40] 

 11.9 — 14.2 



III. Magnetic deflection ; heat developed ; charge carried. 

 Hev^ i Nmv' ^heat. J/e^ charge. 



J. J. Thomson. 1897 



Different gases used. 

 Induction coil. 



1 1 0.077- 



IV. Magnetic deflection and electrostatic deflection. 

 Sev = -^- Sev = Fe [Two deflecting forces balanced] . 



Several gases. Induction coil. 



Lenard rays. 



Lenard rays. Induction coil. 



0.077—0.4 

 About 0.3 

 0.22 — 0.27 



6.7 — 9.1 



[20] 



6.32 — 6.49 



e/m 



The symbols 

 corpuscle ; m = 

 netic field ; F= 

 magnetic field. 



from Zeemann effect. 

 ' ' Ultraviolet light discharge. 

 " Edison effect. 

 " Becquerel rays. 



used in the formulte have the following significance : e = charge carried by each 

 mass of corpuscle ; v = velocity ; JSf^ number of corpuscles ; fl"= strength of mag- 

 = strength of electric field ; r = radius of curvature of the rays when deflected in a 



explained by the accidental errors of obser- 

 vation, it is natural to seek its explanation 

 in the assumptions upon which the two 

 methods are based. Both methods employ 

 the magnetic deflection of the rays and as- 

 sume the same relation between deflection 



formed into kinetic energy of translation ; 

 i. 6., retarding forces due to friction or 

 other causes are assumed to be entirely ab- 

 sent. The method has been criticised on 

 that account by Schuster.* The effect of 

 *Wied. Ann., 65, p. 877, 1898. 



