Page:Proceedings of the Royal Society of London Vol 60.djvu/550

514 magnetic force on the motions of oscillating and revolving electrified particles possessing inertia (ions or electrons) in a magnetic field; and it is thus shown that the broadened edges of the line ought, on Lorentz’s view, to be emitting polarised light, viz., plane polarised in directions normal to the lines of force, and circularly polarised in a direction along those lines.

This prediction has been experimentally verified by Zeeman, and has likewise been confirmed by myself. The flame being looked at from a direction perpendicular to the magnetic field, the light which will be dispersed by the grating to form the extended borders of a line is plane polarised, with its electric oscillations normal to the field’s lines of force.

I hope to have the pleasure of communicating an English version of Professor Zeeman’s complete paper to the March number of the ‘ Philosophical Magazine.’

In the course of the development of a dynamical hypothesis* I have been led to express the interaction between matter and ether as wholly arising from the permanent electrons associated with the matter; and reference was made to von Helmholtz (1893) and Lorentz (1895) as having followed up similar views. A footnote in Dr. Zeeman’s paper has drawn my attention to an earlier memoir of Lorentz (1892), in which it was definitely laid down that the electric and optical influences of matter must be formulated by a modified Weberian theory, in which the moving electrons affect each other, not directly by action at a distance but mediately by transmission across the ether in accordance with the Earaday-Maxwell scheme of electric relations. The development of a physical scheme in which such action can be pictured as possible and real, not merely taken as an unavoidable assumption which must be accepted in spite of the paralogisms which it apparently involves,t was a main topic in the papers above mentioned.

The experiments of Dr. Zeeman verify deductions drawn by Lorentz from this view. It might, however, be argued that inasmuch as a magnetic field alters the index of refraction of* circularly polarised light, which depends on the free periods of the material molecules, it must therefore, quite independently of special theory,

f H. A. Lorentz, “ La Thoovie Electromagnetique cle Maxwell, et ses Applications aux Corps Mouvants,” ‘Archives Neerlandaises,’ 1892. Cf. especially § 91.
 * ‘ Phil. Trans.,’ 1894, A, pp. 719—822; 1895, A, pp. 695—743.