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[ 483 ] 

 LXIV. Intelligence and Miscellaneous Articles. 



NOTE ON THE OPTICAL PROPERTIES OF TRANSPARENT BODIES 

 SUBMITTED TO THE ACTION OF MAGNETISM. BY M. VERDET. 



MANY physicists have indicated the relations between the rotation 

 of the plane of polarization produced under the influence of 

 magnetism and various physical properties of transparent bodies. 

 M. De la Rive, in the first volume of his TrctzVe de V Electricity, in refer- 

 ring to the experiments of M. Bertin, calls attention to the fact that 

 the rotation is generally stronger in proportion as the index of re- 

 fraction is greater. Two substances cited in the Table which M. 

 Bertin has inserted in his memoir *, form exceptions to this rule ; 

 these are alcohol and aether, which are more refractive than 

 water, and which, nevertheless, under the influence of magnetism, 

 rotate the plane of polarization of light at an angle considerably less. 

 In commencing my investigation I have had more particularly in 

 view to determine the extent of application of De la Rive's rule, 

 which various reasons, unnecessary to be reproduced here, led me to 

 regard as well founded. I have consequently measured the index of 

 refraction of a considerable number of substances, and I have then 

 compared the action which they exert upon polarized light, when 

 placed l)etween the poles of an electro-magnet. So as only to em- 

 ploy well-defined bodies and such as can be easily obtained of equal 

 thickness, I have operated exclusively upon liquids, and particularly 

 upon saline solutions. My experiments on the whole have not been 

 favourable to the rule which I was endeavouring to verify, and I 

 think that I may conclude from them that there exists no relation 

 between the index of refraction, and that which, for the sake of 

 brevity, 1 may be allowed to call the magnetic rotatory power. The 

 following Table contains the results of a certain number of experi- 

 ments in which the rule proposed by De la Rive is shown to be very 

 evidently in the wrong. 



Average Complete rotation t 

 Nature of the substance. index of produced by a thick- 



refraction, ness of 44 mm. 



Distilled water 1-334 4° 00 



Solution of muriate of ammonia (dilute) .... 1*359 4 45 



„ „ protochloride of tin (dilute) 1*364 5 27 



„ „ muriate of ammonia (concentrated) 1*370 6 29 



„ „ carbonate of potash 1*371 4 21 



„ „ chloride of calcium 1*372 4 55 



„ „ protochloride of tin (dilute) 1*378 6 10 



„ „ chloride of zinc 1*394 5 57 



„ „ protochloiide of tin (concentrated) . 1*424 8 16 



„ „ nitrate of ammonia 1*448 3 44 



Liquid chloride of carbon (C^ CI*) 1*466 5 12 



M. Bertin has ascertained that certain substances, namely, nitrate 



of ammonia and protosulphate of iron, when dissolved in water, 



* Annales de Chim. et de Phys. 3rd series, vol. xxiii. 



t I give the name of complete rotation to the difi'erence of the two azi- 

 muths of the tint of passage corresponding to two opposite directions of 

 the current. 



