on Magnetic Rotatory Polarization in Gases. 433 



markable fact is nevertheless established, — that the magnetic 



rotatory powers of bodies are closely connected with their 



index of refraction n, and that the variations of the function 



n 2 (n 2 — 1) are of the same order and magnitude as those of the 



magnetic rotations of bodies in the solid, liquid, and gaseous 



conditions. 



In concluding this memoir, I think it necessary to lay stress 



n 2 (n 2 — 1) 

 on the theoretical interpretation of the formula — ^—» -, 



which, according to these researches, seems to intervene in 



the expression of the magnetic rotatory power of bodies. It 



n 2 — 1 

 can be written 2 ; under this form the denominator repre- 



G) 



sents the wave-length of the luminous vibratory movement 

 inside the body studied. The rotation of the plane of polari- 

 zation of the light would be therefore in the inverse ratio of 

 the square of this wave-length, and would be proportionate to 

 the expression n 2 — 1, which, according to the theoretical views 

 of Fresnel and the experiments of M. Fizeau, measures the 

 partial influence of the undulatory movement of a body on the 

 luminous waves. 



It is interesting to note that experiment leads to this same 

 expression to measure the action of magnetism on the propa- 

 gation of luminous vibrations through bodies, thus establishing 

 a new relation between a mechanical effect and the effects of 

 electromagnetic influence. Perhaps this influence of lumi- 

 nous waves on the vibratory movement so well studied is of a 

 kind to inform us as to the mode of motion which manifests 

 itself to us under the form of electricity and magnetism. 



Conclusion. 



The results established in this memoir are as follows: — 



1st. Bodies in a gaseous condition possess, like solid and 

 liquid substances, the property of deflecting the plane of po- 

 larization of luminous rays passing through them when they 

 are submitted to the influence of magnetism. 



2nd. The magnetic rotations of the planes of polarization 

 of rays of different wave-lengths traversing the same gas 

 (oxygen excepted) are generally very nearly in the inverse 

 ratio of the squares of the wave-lengths of the luminous rays 

 considered. 



3rd. The magnetic rotatory powers of gases can be compared 

 with that of liquid carbon bisulphide, and consequently with 

 those of other solid and liquid bodies. 



