428 Dr. H. Stanley Allen on Optical Rotation, 



that the vibrations of the electron which give rise to the 

 rotatory effect are motions of systems of electrons united 

 together by certain forces which are such that a couple of 

 electric forces produces a displacement of the positive 

 electrons in one direction or of the negative electrons in the 

 opposite direction along the axis of the couple" (Schuster). 



In the last few years several mathematical physicists, 

 notably Born * and Gray f, have developed the latter hypo- 

 thesis, and have shown that the optical activity of liquids and 

 gases can be explained by regarding the molecules as 

 coupled systems. Born views a molecule as a system of 

 coupled electrons, the coupling and the restoring forces : 

 being identical. In the paper by Gray the atom is looked 

 upon as a particle of dielectric. The atoms are coupled 

 according to the ordinary laws for a doublet, and the 

 restoring force on an electron is not identical with the 

 coupling, but may be influenced by it. 



To the present writer it appears that a simpler and more 

 realistic mental picture of optical activity may be obtained 

 by abandoning the limitation that the dimensions of the 

 electron must be very small, and employing the ring-electron 

 or "magneton" of A. L. Parson J. Such an electron 

 vibrating backwards and forwards along a straight line 

 seems admirably adapted to rephice the electron moving in 

 a spiral path as imagined by Drude. 



The Ring-Electron. 



The ring-electron may be looked upon as a charge of 

 negative electricity distributed continuously around a ring 

 which rotates on its axis with high speed, and therefore 

 behaves like a small magnet. In an important paper on the 

 electromagnetic mass of the Parson magneton, Webster § 

 has shown that the ratio of the radius of the cross- section of 

 the ring to that of the ring itself is extremely minute, and 

 that most of the energy and momentum of the field are 

 concentrated very closely around the ring. Thus, to a first 

 approximation., the ring-electron may be legarded jis a 

 current in a circular wire of negligible thickness. In a later 

 paper || it is shown that the gyroscopic effect of the magneton 



* Born, Phi/s. Zeitschr. vol. xvi. p. 251 (1915) ; Ann. der Physik, 

 vol. lv. p. 177 (1918). 



+ Gray, Plrys. Rev. vol vii. p. 472 (1916). 



X A. L. Parson, " A Magneton Theory of the Structure of the Atom,"' 

 Smithsonian Misc. Coll. No. 2371, Nov. 1915. 



§ Webster, Phvs. Rev. vol. ix. p. 484 (1917). 



|| Webster, Phys. Rev. vol. ix. p. 561 (1917). 



