( 297 ) 



Pig. C. General arraitgeitu-nt of the mirror-readbig. K telescojie, L graduated 



glass scale, illuminated by the minor-strips Q, M intermediate mirror, 

 -A'' reading mirror. 



Fig. 7 and S. Ilomding of tlic mirror on the mit in the flange of the smaller nicol- 

 bearer. rl nnt, X and J' two rings, Z tastening-screws, .V reading-mirror. 



Fig. 9. High-pressure conduit. J" cylinder with compressed gas, ^ high-pressure 



stopcock for closing the former, B stopcock for closing the mano- 

 meter, C and J) stopcocks for drawing oft' the gas, T connection T\itli 

 the experimental tube. 



Fig. 10. High-presivre Hapcoch. See J, B, C and 1) of the preceding figure. 



Fig. 11. Sections of the tides for the circulation of water together with thermo- 



meters, i i tubes in sections, /-j supply, I.:^ outlet, l^ and 7; thermo- 

 meters, z'i, and »«2 nuts. 



Fig. 12. Curves of the rotaton/ constants. See furtlier on. 



2. Formulae for interpolation of different forms. It has been 

 stated in a previous communication ^) that the different theories of 

 tlie magnetic rotation lead to two forms of formulae for the rotatory 

 constants of «, viz. 



« = § + ^+ (H) 



With a view to the fact that in the case of oxygen we obtained with 

 the first form a better accordance with the rotatory constants ob- 

 served than with the second form ~), we have published in the later 

 communications only formulae for interpolation of the form (I) with 

 two terms. In the nieantime the continuation of the calculations 

 showed that for nearly all gases the form (II) with two terms was 

 more satisfactory. The contiary proved to hold only for oxygen and 

 for the mixtures of oxygen and niti'Ogen, among which we may 

 mention in the first place air, further a mixture with 87.8 percent 

 oxygen, on which some observations have been made in the be- 



1) A'ersl. Kon. Akad 1S9-1/95 p. 237; Comm. Phys. Lab. at Leiden IS'». 15, p, 27. 

 ') " " " '/ p. 238; /' r „ " ^•^ 15, p. 2S. 



