213 



apparatus. The line thus registrated on the sensitive paper enables 

 us at once to judge by its breadth and blackness of the extinction of 

 the substance. 



As well with ex-solid as with ex-Iiqnid the teniperatnre appeared 

 to exercise a plainly perceptible influence on the extinction, but the 

 direction of the effect is for the photographically active rays just 

 the reverse as for the ultra-red rays, i.e. for tlie short waves at 

 rising temparature the extinction increases. So, as the effect of the 

 temperature in the case of strongly differing wave-lengths has 

 a right to a different sign, the apparent contradiction between the 

 resnlt of Schenck and that which follows from our extinction-curves 

 is explained. 



§ 2. The influence of a magnetic field on the extinction. 



The fact that there appeared to exist two liqnid-crystaliine states, 

 made it desirable to extend our research on the influence of mag- 

 netic field to the second states. Besides the magnetic effect on the 

 three remaining substances we disposed of, had to be examined. ') 



With p-benzoë-acid azoxy aethylester no influence could be esta- 

 blished, not even with the strongest fields we could excite, (ca. J 100 

 Gauss). An examination with still stronger magnetic field is being 

 prepared now. Anisaldazine experiences a strong influence as well 

 in ex-solid as in ex-liquid slate. With p-azoxy-phenetol the influence is 

 much weaker, but could still be observed by us with certainty in 

 both states. The character of the effect is for both substances prin- 

 cipally the same as for p-azoxy-anisol. 



The magnetic effect of p-azoxy-anisol in the ex-solid condition is 

 represented by the figures 3 and 4. For sake of comparison we 



Fig. 3. P-azoxy-anisol 



ex-solid 



vertical field (1100 Gauss). 



1) In our first communication we mentioned the preponderating influence the 

 nature of the adjacent surface lias on the magnetic effect. In order to examine 

 this influence more closely we have registered the magnetic effect, for substances 

 of different thickness, put between glass whether or no chemically cleaned, or 

 enclosed between mica. The differences found, however, were only of quantitative 

 character. 



