658 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



In fig. 96 the source is supposed to be at a finite distance and the 

 section normal to the axis. The maximum phase-difference is that 

 between the two rays that lie in the plane of the optic axes ; in the 

 figure, this plane is taken as the plane of the paper. It can be shown 

 that the phase-difference at the point of interference is constant if the 

 rays are so nearly parallel to the axis that their front velocity in the 

 crystal may be considered constant. When the section is not cut normal 

 to the optic axis (as in fig. 1)5) the same result holds if the thickness 

 parallel to the axis be considered instead of the section thickness. From 

 certain experimental data the author concludes that the behaviour of 

 the crystal in light that is approximately parallel to an optic axis, must 



V 



/ 



Fig. 95. 



1 

 5 



Fig. 96. 



be referred to interference effects of exactly the same nature as those 

 observed in any general section with the light falling at any inclination 

 to the axis. 



Axial Images of Fluid Crystals.* — D. Vorlander and H. Hands- 

 waldt have published the results of their investigations on the above 

 subject. These results are illustrated by 19 plates containing about 80 

 beautiful photographs of interference figures which have been all 

 obtained bv examination with polarized liijht of thin lavers of certain 

 fluids. These figures seem a proof of the crystalline composition of 

 fluids, and they suggest an insight into the structure of fluids and of 

 molecules. They are met with not only in simple forms, but in com- 

 plicated designs identical with those of solid crystals. At present, 

 however, only uniaxial varieties have been detected. 



Ultramicroscopic Examination of Liquids during Electrolysis.f 

 J. J. Kossogonoff (of the University of Kieff) has thought of using 

 the ultramicroscope invented by Siedentopf and Zsigmondy for the 

 investigation of the phenomena of electrolysis, with extremely good 



* Abhand. der Kais. Leopold-Carolin, Deutsch. Akad. der Naturf., xc. pp. 

 105-17 (19 pis.). t Athenteum (1910) ii. p. 73. 



