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and its Relation to the Quantum Theory, 851 



spherical symmetry demanded by the Coulomb law *. One 

 way to account for the magnitude of the observed dis- 

 symmetry is to assume that the electron is a magnetic doublet 

 of strength about 10 " 20 E.M.U.* (such as would be produced 

 by a rotating ring of electricity having one quantum unit 



5— of angular momentum). However, the strength of the 



magnetic doublet would have to be about 5 x 10~ 19 E.M.U., 

 a value fifty times as large as that given above, in order 

 to have the desired effect on the ionization potential of helium. 

 The existence of a magnetic doublet of such a large size could 

 not be reconciled with observed molecular magnetic moments, 

 which are very much smaller, and would invalidate the 

 classical theory of the scattering of X-rays, as the magnetic 

 forces acting on this magnetic electron would be com- 

 parable with the electrical forces when the wave-length of 

 the impressed beam of light did not exceed the atomic 

 diameter. It is doubtful whether it is possible to attribute 

 to an electrical or magnetic origin departures from the 

 inverse square law of sufficient magnitude to explain the 

 anomalies of normal helium. Instead it would be necessary 

 to introduce a "mystery force,'' which is negligible except at 

 atomic distances, and which does not have a mechanism based 

 on the Maxwell field-equations. This new force should 

 explain the spiral tracks of beta particles as well as the 

 properties of helium. In support of the idea of introducing 

 this rather arbitrary "' mystery force," it should be stated 

 that it is not improbable that such a bold hypothesis may be 

 necessary in order to explain the stability of atomic nuclei. 

 A cogent argument against modification of the law 7 of force 

 between negative electrons is that it cannot account for the 

 absence of a satisfactory model of the positively charged 

 hydrogen ion, which contains only one electron. Also a 

 simple computation shows that a mystery force between elec- 

 trons depending only on their relative distance (consequently 

 developable in a series in inverse powers of the distance) 

 would invalidate the Sommerfeld-Kossel theory of X-rays f, 



* A. H. Compton, Phil. Mag. vol. xli. p. 279, Feb. 1921. 

 t This follows as a consequence of the fact that centrifugal force 

 h- . . h 



mll(ft-= t-t z — ps acting on an electron having one quantum unit :> _ 



of angular momentum varies inversely as the cube of the radius as 

 the latter changes from element to element in the K ring. Then fore 

 an inverse cube mystery force comparable with the centrifugal force 

 in the helium atom, so as to give the required alteration in the 

 ionization potential, would also be comparable with the centrifugal 

 force in the K rings of elements of higher atomic number, and hence 

 would have an appreciable effect on the energy. With mystery forces 

 involving higher inverse powers, the effect would be even larger. 



