The progress of physics during 33 years (1875-1908) : four lectures delivered to the University of Calcutta during March 1908 / by Arthur Schuster.

  • Arthur Schuster
Date:
1911
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Licence: In copyright

Credit: The progress of physics during 33 years (1875-1908) : four lectures delivered to the University of Calcutta during March 1908 / by Arthur Schuster. Source: Wellcome Collection.

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    is found that the velocity of propagation of electro- magnetic effects is equal to that of light. Hence we can calculate the velocity of light, making use only of purely electric measurements. This is convincing, and leaves no reasonable ground for doubting, that light and electrical actions are both transmitted through the same medium : that light is in fact an electro-magnetic phenomenon. In his first endeavour to develop Faraday’s theory of electric action, Maxwell went beyond the necessities of the case, so far as the electro-magnetic theory of light is concerned. The scientific period of which I am speaking was essentially one of model making. Physicists still felt the necessity of having clear con- ceptions, and distrusted mathematical symbols that had no fully defined meaning. If the aether be called upon to transmit electric and magnetic actions, scientific men felt uncertain of their ground, unless they had some notion how the necessary stresses and strains were brought about. Hence Maxwell, who unquestionably belonged to this school, which requires a mechanical model for the conception of physical phenomena, devoted a good deal of time to the specification of electrostatic and magnetic strains in his medium. It is not necessary to enter into that part of his work here, because the question has for the moment been pushed into the background ; nor is it necessary to enter into the successes, which the electro-magnetic theory soon achieved by overcoming the difficulties of the older theories of light. The issue on which Maxwell’s results went consider- ably ahead of experimental knowledge was the trans-