10 compton: size and shape of electrons 



magnetized to that when unmagnetized should be approxhnately 



K'-y -ft) 



where a is the radius of the ring electron and k is the fraction 

 of the electrons which are oriented by the magnetic field. Using 

 the value a = 2.3 X 10~^" cm., this means that the change in 

 the absorption due to magnetization for X = 1.0 X 10 ~^ cm. is 

 0.7 k per cent, and for X = 0.5 X 10^^ cm. is 2.8 k per cent. 

 From the observed values of this difference we find that the 

 fraction of the electrons oriented by the magnetic field is 0.6 

 and 0.26. The experimental basis of the latter value is much 

 the more certain. Taking the number of electrons in the iron 

 atom to be 26, this means that in order to explain Forman's 

 effect in terms of ring electrons a number 0.26 X 26 = 7 of the 

 electrons must be capable of being oriented by the magnetic 

 field. This is what would be expected if it is the 8 valence 

 electrons of iron which are responsible for its ferro-magnetic 

 properties. Our hypothesis of a ring electron of radius 2.3 X 

 10~i^ cm. is therefore capable of explaining satisfactorily For- 

 man's effect. 



It should be noted that Forman explains his effect as be- 

 ing due to an orientation of the molecules in the iron. The 

 experiments of Rognley and the writer'^ on the effect of mag- 

 netizing a crystal on the intensity of the beam of X-rays re- 

 flected by it have shown that any orientation of the molecules, 

 if it occurs at all, must be extremely small. It was found fur- 

 ther that unless it is very nearly isotropic the atom also is not 

 rotated by magnetization. Thu^ Forman's explanation of his 

 effect is inadequate. The fact that his experiments can be ex- 

 plained in terms of an orientation of the electrons must be 

 taken as a confirmation of the conclusion arrived at by Rognley 

 and the writer that it is not the atom as a whole, but the electron 

 itself that is the ultimate magnetic particle. 



18 Compton and Rognley. Science (N. S.) 46:415. 1917. 



