( 738 ) 



2) At — 79° file bands were already considerably widened and 

 faded so that (he thicker ruby plate had to be investigated through which 

 the light proceeded 7 mm. in the direction of the axis. 



Heating from —193^ to — 79^ displaced R,byO,Q2^iA, R^0,58n(i 

 towards the red so that their distance now became 1,42 (ah. In a field 

 of 18,5 kgs. R^ exhibited a lefthand break of 0,12, .ufi, a righthand 

 one of 0,065 (in, and R.^ deviated 0,04 on the left, 0,07 n n on 

 the right. 



3) At -f 18° and a field of 18,5 kgs. R, exhibited a break of 

 0,07 (1(1 towards both sides, R^. one of 0,055 (i(i. Heating from 

 — 193° to +18° shifted R,0,7Q(i(i, /?, 0,69 ,i/t towards the red, 

 so that their distance now became 1,45 (in ^). 



4) At -{- 200° the phenomenon was rather vague. By estimation 

 the two lines showed a symmetrical break of 0,04 (i(i with 18,5 kgs. 

 Heating from 18° to 200° moved both R^ and R^ 1,1 (i(i towards 

 the red, their distance therefore not being changed. As yet we have 

 not heated the ruby any higher. 



In general we may perhaps conclude from the rather intricate course of 

 the phenomenon that the influence of magnetisation slightly decreases 

 with increase of temperature. The distance between R^ and R^, on 

 the otiier hand, seems to become a little larger. 



§ 17. We now proceed to the second case: 



II Optical axis ± direction of field, where we 

 must distinguish the ordinary and the extraordinary spectrum. In 

 this case only the nicol, no longer the double ^4 pl^^^ was used, 

 because circular polarisation does not come in here. 



1 . Ordinary spectrum ; plane of polarisation horizontal : 



A. Pair of hands in the blue at —193°. The width with field 

 off amounted to 0,17 for B^^ to 0,14 (i(i for B^, the distance of the 

 central lines being i ,68 n(i ; the lines looked about equal : In a 

 field of 36 kgs. the width increased to 0,26 /nft for the two lines; 

 half the increase in width amounted therefore for B^ to 0,045, for 

 5, to 0,06 (1(1. 



B. Pair of bands in the red at — 193°. We have (cf. § 7) 

 /?, == 691,8 and R, = 693,2. The width with field off amounted to 

 0,08 for R,, to 0,07(1(1 for R^, their distance in the grating spectrum 

 being 1,41 (i(i. 



With a field of 20 kgs. R^ became widened, and seemed shaded 



1) We gave up the idea of reproducing a photograph, because the reproduction 

 in our former paper is greatly inferior in distinctness to our own prints. Moreover, 

 where measurement proves possible, reproduction appears almost superfluous. 



