A TEST FOR ELECTRON POLARIZATION 481 



The question of the result to be expected from the wave theory of 

 the electron in experiments of the kind here described has recently been 

 considered by Darwin.'^ The conclusion which Darwin reaches is 

 that a beam of electrons initially unpolarized will remain unpolarized 

 after diffraction by a grating provided the forces in the grating re- 

 sponsible for the scattering are electric rather than magnetic, and that 

 therefore any experiment designed to detect polarization by successive 

 reflections from crystals can lead only to a negative result. The result 

 of our experiment is in accord with this prediction. 



It is a pleasure to express our best thanks to Mr. G. E. Reitter for 

 the great care with which he constructed the special apparatus used 

 in this experiment, and to Mr. C. J. Calbick for valuable assistance in 

 collecting and reducing the data. 



12 Darwin, Proc. Roy. Soc, 120, 631 (1928). 



