OF THE REFLECTION AND REFRACTION OF LIGHT. 
711 
lead to the same conclusion here—namely, that iron, if transparent, would behave like 
those ferromagnetic substances observed by Verdet, which rotate the plane of 
polarisation in the opposite direction to the Amperean currents, as is of course most 
probable. He further mentions, in § 24, that the phase of this component is always 
nearly the same as that of the component of the reflected ray polarised in the plane of 
incidence. This question, however, of difference of phase is one I am not at present 
prepared to explain, and, as I have mentioned already, must await a more compre¬ 
hensive theory. Considering next the intensity, of course no very accurate measures 
were possible on account of the minuteness of the phenomenon ; but he several times 
remarks that all effects of magnetisation vanished at normal and grazing instances, 
while his maximum effects were always obtained at incidences of about 60° or 65°. 
The anomalies observed connected with the incidence 75° all belong to the question of 
the difference of phase between the components, which my investigation does not 
touch. On the whole then I think that my results, as far as they go, are in complete 
accordance with Mr. Kerr’s experiments. 
This investigation is put forward as a confirmation of Professor Maxwell’s 
electromagnetic theory of light, in which, though there are some points requiring 
further investigation, nevertheless the foundation has certainly been laid of a very 
great addition to our knowledge, and if it induced us to emancipate our minds from 
the thraldom of a material ether might possibly lead to most important results in the 
theoretic explanation of nature. 
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