60 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



unlikely that it could be due to any simple rectilinear arrangement of 

 unit magnets or current circuits, such as N|S — N|S — N|S — NjS, 

 etc., which is the only conception of the atom's structure that could 

 give Weiss' magneton any structural significance. 



§18. The Possibility of Detecting the Magneton Directly: 

 The Heat of Dissociation of Hydrogen 



That the magneton has never yet been detected directly by its 

 magnetic moment is not at all surprising, for a consideration of the 

 possibilities shows that this is either beyond or just at the limit of the 

 present experimental resources. 



First, in kathode rays : We have for the force which produces the 



familiar deflection across the lines of magnetic force : 



.£f>z/ = // X 1 .57 X io -20 x 3 X 10 9 



= H x 5 X io -11 dynes. 



Now the force on the magneton due to any non-uniformity in a 



magnetic field through which it passes is 



dH ,, dli iq , 



-^ . M = -^ X 3.5 X io" 19 dynes. 



Seeing that in experiments on kathode rays, H has been perhaps 500 

 gauss, and that a gradient —j— can scarcely be made to exceed 



CIS 



50,000 gauss per cm. by any means whatever, it is obvious that the 

 second force is too small ever to be detected by any deflection of 

 kathode rays. 



Another line of attack is more promising. If the electron has a 

 magnetic moment, we may expect to be able to increase the concen- 

 tration of electrons in an earthed conductor by setting up a magnetic 

 field over it. In this case we can calculate the potential reached ( V) 

 by equating the electric work gained with the magnetic work lost for 

 the movement of each magneton. 



Ve 



— = HM. 

 2 



T . 2X3.5XFO" 19 



•■ V = Hx 1.57x10" 



= HX4S E - M -U. 



= HX4.5Xio~ 7 volts. 



Now over a conductor of such a size and situation as to have a 

 reasonably great capacity (such as io E. S. U.), it is difficult to set 

 up a magnetic field of more than 1,000 gauss. Assuming this field, 



