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Abstract

Two subjects of philosophical and physical investigation have excited deep interest during recent years, the theory of relativity and the theory of quanta. These were discussed by Dr. J. H. Jeans in his Kelvin Lecture on “Electric Forces and Quanta,” delivered on February 5 at the Institution of Electrical Engineers, and published as a special supplement to this week's issue of NATURE. The first part of the lecture deals with electric forces in the light of the theory of relativity, and it is claimed that, as all the phenomena go on as though there were no ether, the conception of an ether is superfluous. If an ether does exist, it must probably be thought of as a four-dimensional structure and must be largely subjective. The generalised geometry of Einstein and Weyl can predict and explain all the systems of forces of the universe, both gravitational and electrodynamical. But geometry does not explain the atomicity of electric charges or the essential difference between positive and negative electricity. Again, quantum theory indicates the existence of discontinuities in Nature of a kind not contemplated in the older mechanics. No one is better qualified to deal with the implications of this theory than Dr. Jeans, whose report on radiation and the quantum theory published by the Physical Society of London has long been a mine of information for those interested in the subject. Some of the ideas adumbrated in the final chapter of that report have now been developed further. It may well be that the atomicity of the quantum theory is only another aspect of the atomicity of electric charges. The quantum theory represents, perhaps, a quality of the four-dimensional continuum, which is somehow analogous to the scaliness of a crocodile skin. This is equivalent to the suggestion that the “calamoids” or four-dimensional tubes of force of Prof. Whittaker should be regarded as quanta. Our conception of the action of an electric field on an electron seems to require revision in the light of a recent hypothesis due to Einstein. The electric forces in Maxwell's equations serve in some way to measure the probabilities of jumps in the velocity and perhaps also in the position of an electron in an atom.