1906] LORENTZ— ON POSITIVE AND NEGATIVE ELECTRONS 109 



invalidated by some new hypothesis, we need no longer continue our 

 comparison of the two theories ; we ought surely to give up all 

 attempts to explain phenomena by the assumption of two kinds of 

 movable electrons. I shall only adduce one argument more, which 

 may be drawn from what is known of the so-called canal rays and 

 the a rays of radioactive bodies. The positive electrons which con- 

 stitute these rays have been found to have a mass of the same order 

 of magnitude as that of the chemical atoms, a fact which lends a 

 strong support to the view that in a metal the positive charges are 

 rigidly fixed to the material atoms and that only the negative elec- 

 trons can freely move over considerable distances. 



As to the Hall-effect, which at first sight seemed to speak so 

 strongly in favor of the two fluids theory, we shall have to examine 

 whether it cannot be accounted for by the motion of -negative elec- 

 trons only. If we succeed in this, as perhaps we can by going some- 

 what deeper into the mechanism of the phenomenon than we have 

 done in our somewhat superficial discussion of it, we shall after all 

 come to a system of explanations much resembling Franklin's uni- 

 tarian theory of electricity. 



Leiden, April, 1906. 



