a Hays from liadium and Polonium. 515 



were applied in one direction only ; the inner narrow line is 

 the undeflected beam, and the other narrow line the deflected 

 a beam. Thus it will be seen that the dispersion cannot be 

 much more than 10 per cent, of the deviation. If there were 

 different kinds of particles sent out by the radium, the lesser 

 dispersion in the electric field than in the magnetic field 

 would be explained if the energies of the different kinds of 

 particles were much more nearly the same than their momenta, 

 as these are the physical qualities involved in the two cases 

 respectively. 



The wide fuzzy line in figure 4 on the opposite side of the 

 central line from the deflected a. rays must be due to j3 rays. 

 Thev are deflected about two or three times as far as the 

 cc rays. If they are j3 rays from the radium itself, they must 

 be exceedingly rapid and have a velocity nearly that of light; 

 but they may be secondary /3 rays. Further investigation 

 is needed before one can state their real source. 



11 IV 



We have thus for the average ray =4 , llxl0 14 , and 



= 3-00 x 10 5 ; whence the average v = l'37 x 10 9 cm. per 



e 



at 

 sec, and — =1*6 X 10 3 electromagnetic units. 



above for — in the magnetic deflexion experiments, and 



The extreme velocities would be from the values given 



lIlV 



e 



assuming no dispersion in the electrostatic observations, 

 I'll x 10 9 and 1*64 X 10° ; or, increased by 6 per cent, to 

 allow for the absorption by the mica, we have for the slowest, 

 the average, and the fastest a. rays leaving the surface of a 

 small quantity of radium (12 mgr.) the velocities 1*18 x 10 9 , 

 1*45 x 10 9 , and 1'74 x 10 9 cm. per sec. respectively, about 

 -^q of the velocity of light. To be compared with my value 

 of v=\'M X 10 9 are Rutherford's earlier estimate of 2'b x 10 9 

 and Des Coudres' value of 1*65 x 10 9 . My value of T74 x 10 9 

 for the fastest rays observed is decidedly less than that 

 deduced by Rutherford in his paper on the rays from 

 radium C ; viz., 2'() x 10°. 



£ 



The value of — =4'6 x 10 3 is much smaller than the values 

 m 



previously found by Rutherford and Des Coudres, which lay 

 between 6 and 6*5 x 10 s . Assuming that the charge on the 

 « particle is the same as that carried by the hydrogen atom, 



for which the value of — is 10 4 in the units used above, Ave 

 m 



Phil. Mag. IS. 6. Vol. 10. No. 59. Xov. 1905. 2 P 



