Iv] NATURE OF THE RADIATIONS VALI 
For the cathode rays S. Simon! obtained a value of e/m of 
1:86 x 10’ for an average speed of about 7 x 10° cms. per second. 
In a later paper? with some very active radium, more satis- 
factory photographs were obtained which allowed of accurate 
measurement. The given equation of the curve was found to 
agree satisfactorily with experiment. 
The following table, deduced from the results given by 
Kaufmann, shows the agreement between the theoretical and 
experimental values, wu being the velocity of the electron and V 
that of light. 



Value of Observed value of | Percentage difference 
u m from theoretical 
V my values 
Small 1 
"732 1:34 -15% 
“752 1:37 —0°9,, 
UAT 1°42 -—06,, 
801 1:47 +0°5,, 
830 1°545 +0°5 ,, 
*860 1°65 OR... 
883 1°73 +2°8 ,, 
933 2°05 —78,, ? 
949 2°145 —12,, 
‘963 2°42 +0°4 ,, 




The average percentage error between the observed and calcu- 
lated value is thus not much more than one per cent. It is 
remarkable how nearly the velocity of the electron has to approach 
the velocity of light before the value of — becomes large. This. 
0 
is Shown in the following table which gives the calculated values 
of as for different velocities of the electron. 
Lo 
Value of = small oj 5 9 ‘99 -999 -:9999 999999 
Caleulated m 469 1.015 112 181 328 496 668 10:1 
value mp 
Thus for velocities varying from 0 to 1/10 the velocity of light, 
1 Wied. Annal. p. 589, 1899. 
2 Phys. Zeit. 4, No..1b, p. 54, 1902. 
