324 Prof. Rutherford and Mr. Grier on Deviable 



The uranium from which the active fraction had been 

 removed by the three methods was found almost completely 

 free from deviable rays, while the non-deviable rays were not 

 much reduced. Not a trace of deviable rays was obtained 

 from uranium after 12 precipitations with barium sulphate, 

 although J per cent, of the original amount could have been 

 readily detected. We thus see that by different chemical 

 methods the part responsible for the deviable radiation in 

 both uranium and thorium can be separated from the main 

 body, while part at least of the non-deviable radiation is 

 unaffected. 



§ 7. Other Results. 



No trace of deviable rays could be detected by the electric 

 method from polonium. This is in agreement with the re- 

 sults of Becquerel by the photographic method. We have 

 so far been unable to obtain any conclusive evidence of the 

 existence of deviable rays in the emanation of thorium, 

 although the emanation gives off strong non-deviable rays. 



§ 8. Penetrating Power of the Deviable Rays. 



By noting the diminution of magnetic effect in the testing- 

 cylinder when successive layers of thin aluminium or tinfoil 

 were placed over the radioactive substance, the penetrating- 

 power of the deviable rays can be compared. 



When the magnetic effect falls off in geometric progression 

 with the thickness the rays may be supposed to be fairly 

 homogeneous in character. If the absorption is greater for 

 the first few layers than for succeeding layers, the rays are 

 complex, i. e. the rays are made up of streams of electrons 

 differing in velocity, and consequently in penetrative power. 



Tested in this way it was found: 



(1) That uranium, and the excited radioactivity due to 

 thorium, gave out deviable rays approximately homo- 

 geneous in character and of about the same penetrating 

 power. 



(2) Thorium and radium both gave out very complex rays. 

 This has been shown by Becquerel for radium, using the 

 photographic method. He found that the magnetic 

 deviation of the rays varied within wide limits. 

 Thorium X gives out a large proportion of easily ab- 

 sorbed deviable rays. 



(3) Radium and thorium and the excited radioactivity due 

 to them all emit some deviable rays of about the same 

 penetrating power as those from uranium. The rays 

 from uranium pass through about '5 mm. of aluminium 

 before the intensity is reduced to one half. 



