Homogeneous ^-Particles of Different Velocities. 869 



The first column gives the values of Up. The following 

 three columns give the ratio of the ionization produced by 

 multiple reflexion to the ionization produced by the incident 

 rays for lead, copper, and carbon respectively. The last 



Ffc. 2. 



2700 3600 4500 



Hp in gauss cm. 



8100 



column gives the ratio of the values for lead and copper as 

 obtained from the smooth curves. This ratio is roughly 

 constant, indicating that the changes of reflexion with the 

 velocity are proportional for the two substances. The ex- 

 periments with carbon were difficult on account of its weak 

 reflecting power, and the results are consequently subject to 

 greater errors than in the case of the other two substances. 

 The experiments with an angle of 30° for the inclination of 

 the ionization vessel with the horizontal were tried with lead 

 only, and the results were materially the same as for 45° 

 inclination. For the very slowly and very rapidly moving 

 /3- particles the experimental errors are greater on account 

 of the fact that the /3-ray effect is small compared with 

 the 7-ray effect, since the distribution of the number of 

 /3-particles with the velocity gives a maximum and decreases 

 quite rapidly on each side. This accounts for the irregu- 

 larity of the observations at both extremities of the smooth 



curve. 



The results here obtained fully confirm the results of the 

 investigation with the heterogeneous rays from radioactive 

 bodies as given in the preceding paper. It will be observed 

 that the diffusely reflected radiation as measured by the 

 ionization rises rapidly to a maximum and then slowly begins 

 to fall. If the /3-particles were reflected with the same 

 velocity with which they impinge on the matter, or if the 



