on Magnetic Rotatory Polarization in Gases. 431 



first column and those in the third, we may construct a curve 

 by taking the indices as the abscissae and the rotations as the 

 ordinates : in this way a curve of great regularity is obtained, 

 whose form recalls that which we obtained under analogous 

 conditions with liquid and solid bodies (fig. 5). 



By seeking a simple function of the index, which varies 

 proportionately to the rotations observed, we easily see that 

 the ratios of the function (n — l) 2 , n being the index of re- 

 fraction, follow very nearly those of the magnetic rotations. 

 These appear in columns 2 and 4 of the preceding table. 

 However, it does not seem that this formula is the complete 

 expression of the relation between the magnetic rotatory 

 powers of bodies and their indices of refraction. We had 

 already observed that it did not suffice for the various peculia- 

 rities of the phenomenon in solids and liquids ; and it is easy 

 to see that it does not account for the relation of the magnetic 

 rotatory powers of bodies in the liquid and gaseous conditions. 



In my previous researches, I had been led to adopt the ex- 

 pression n 2 (n 2 — 1) as approximately representing the state- 

 ments of the magnetic rotatory powers of the various solid and 

 liquid bodies that had been studied. I had discovered that 

 the relation of the magnetic rotation R to the function 

 n 2 (n 2 — 1) varied very little when compared with the great 

 variations of the magnetic rotations of one body and another. 



The unit adopted was the magnetic rotation of liquid carbon 



bisulphide ; and the values of the expression 2 2 _i\ (gene- 

 rally about 0*25) varied between 0*10 and 0*50*. These 

 yalues are indicated in column 5 of the preceding table. The 

 numbers obtained are the same as for various solid and liquid 

 bodies. Thus, although the magnetic rotations are 10,000 

 times smaller than in liquid bodies, the variations in the func- 

 tion n 2 (n 2 — l) are always of the same relative order of size 

 as those of the magnetic rotations. 



It ought, however, to be observed that the numbers in the 

 fifth column of the preceding table increase regularly with the 

 indices of refraction, which tends to prove that the formula 

 n 2 (n 2 — 1) is only an approximate expression of the pheno- 

 menon, which answers sufficiently well for the properties of 

 non-magnetic solid and liquid bodies, but which might diverge 

 from experiment when the values of the index of refraction 

 became very small, as in the case of gases. 



The variations of the expression 9/ 9 — r>- with gases do 

 r n\nr — 1) 



* See the researches quoted above. 



2K2 



