on Magnetic Rotatory Polarization in Gases. 399 



in the same way as for my experiments with the gases. The 

 luminous rays passed through the glasses several times ; and 

 their plane of polarization experienced unequal magnetic 

 rotations, which were measured for each image. 



Magnetic Rotations of Carbon Bisulphide, with different 

 luminous Sources. 





Magnetic ro- 

 tations com- 

 pared with 

 that of yellow 

 light D. 



Average. 



Average length 



of wave deduced 



from the 



rotations. 



series. 



[2nd 

 Eed glass, No. 1 {3rd 



I 4th 



f2nd 

 Eed glass, No. 2 \ 3rd 



[4th 

 Yellow rays D 



fist 

 Yellow glass \ 2nd 



[3rd 

 White light, incandes- 1 -, , 

 cent lime J 



rist 



0-8121 

 0-803 L ... 

 0-809 J 

 0-838 1 

 0-824 I... 

 0-847 J 

 1-000 

 0-968 1 

 1-080 L... 

 1028 J 



1-066 



1-3321 



1-232 1 

 1-245 f- 

 1-287 J 

 1-4581 

 1-498 I... 

 1-482 J 



0-808 

 0-836 



1028 



1-274 



1-480 



645-0 



634-5 



589-2 

 582-0 



571-5 



528-5 



500-0 



[4th 

 f2nd 



[4th 



The following Table contains the results obtained. In order 

 to facilitate the comparisons, the numbers observed were re- 

 duced to what they would be with the intensity of the electric 

 current which I employed as unity throughout the work ; but 

 as they arise from more considerable rotations, their precision 

 is greater. The results are given to the hundredths of a 

 minute ; at best the tenths of a minute can be relied on. In 

 this Table I have been obliged to make some corrections, 

 Avhich will be justified later — in particular the action of mag- 

 netism on the column of air subjected to the action of the 

 electromagnetic coil, and the influence exerted by the latter 

 on the glass of the nearest mirror. 



Finally, as the law of dispersion of the planes of polari- 

 zation of the various coloured rays is ascertained for the 

 crown glass, the approximate value of the average wave- 

 length of the luminous rays which reach the eye for each 

 image can be reduced from the observed rotations. 



2H2 



