a Particles from Thorium Active Deposit. 705 



due (a) to small errors in the measurement of I — this error 

 being increased in Z 2 , (b) to slight differences in the mag- 

 netizing currents, or to the iron being in a non-cyclic state 

 in some of! the experiments. 



Fiff. 2 



1-2 



10 



$0-6 

 ■♦3 



I 

 •3 



0-4 



0-2 



B 



I* 



12 



20 



For the calculation of the ratio of the velocities, only the 

 photographs showing a deflexion greater than 0'5 cm. with 

 reversed fields have been used. 



All deflexions were measured by means of a travelling- 

 microscope reading directly to O005 mm. and by estimation 

 to 0*001 mm. Measurements have been made from ten of 

 the best of thirty photographs, from 20 to 50 sets of obser- 

 vations being taken in each case. 



The results of typical measurements are given in Table I. 

 The magnetic fields used in these cases varied between the 

 limits 9,400-10,500 gauss, the variations of deflexion being- 

 produced by varying /, the distance from source to slit or 

 from slit to photographic plate. 



