Convection on Optical Rotatory Polarization. 369 



fact, merely a paraphrase of Prof. Lorentz's argument (Proc. 

 Amst. Acad. April 19, 1902). 



The conclusion to be drawn from Lord Rayleigh's result 

 may thus be held to stand as before, that in the more complex 

 circumstances of rotational media as well as in ordinary optical 

 propagation in matter, the ions or electrons that form the 

 connexion between the matter and the ?ether interact in all 

 their relations according to laws of purely electrodynamic 

 type. 



The single principle that electrification is of atomic cha- 

 racter, with or without a distinct material basis, so that when 

 the medium is convected the ions belonging to it exert the 

 ordinary electrodynamic influence of moving charges, suffices 

 to abolish all first-order effects of uniform convection on the 

 electric and optical properties of material media ; rotational 

 optical phenomena being therein included. It is only when 

 the absence also of second-order effect of uniform convection 

 has to be accounted for that more questionable hypothesis 

 must enter. It appears to be established that, if it could be 

 granted that the molecules of matter are constituted entirely 

 on an electric basis, no second-order effects either electric or 

 optical would arise. Such an electric basis of matter implies 

 that, an ordinary molecule being made up somehow of a group 

 of ultimate atoms describing steady orbits round each other 

 after the manner of a stellar system, the mutual actions of 

 these ultimate atoms, as also their inertia, are wholly electro- 

 dynamic, and are thus really resident in the interconnecting 

 aether in which the atoms constitute mere singular points or 

 centres of strain. If this hypothesis could be admitted, — and 

 no independent reason can be assigned for its validity, except 

 that fundamental presumption of simplicity which we are not 

 unaccustomed to find justified in physical analysis, — the nega- 

 tive second-order optical observation of Michelson and Morley 

 would be explained. Electric effects of the second order 

 would also be absent ; and there appears to be one such (an 

 outcome of a suggestion of Fitz Gerald's) which would otherwise 

 exist, that in Prof. Trouton's hands will probably furnish an 

 independent experimental test*. 



Although the constitution of a molecule has not been syste- 

 matically elucidated on this purely sethereal hypothesis any 

 more than it has on any other, au increasing tendency to con- 

 sider it as a working scheme maybe remarked f. And in this 

 connexion it may be noticed that there is no necessity for 

 restricting the singularity in the constitution of the aether to 



* See Trouton Trans. Roy. Dub. Soc. vii. (1902) ; also FitzGerald's 

 1 Scientific Papers/ pp. 557, 566, lxi. 



+ E. g. Planck, Berlin. SitzunysbericMe, xxiv. p. 486 (1902). 



