560 Mr. S. A. Shorter on Surface Separation from 



To do this let the large crystal consist of closely packed 

 cubes each of whose edges is 3 X 10~ 3 cm. Let each cube 

 consist of an outer shell of thickness J x 10 -6 cm. and a 

 kernel constituting the rest of the cube. Let the intrinsic 

 strain change from the outside to tho inside of the shell by 

 the elongations gradually passing from the free aether values 

 e , e , e to the proper crystal values e ly f, (j x which are to be 

 maintained uniform throughout the kernel. The double 

 shells separating two neighbouring kernels will behave simply 

 as thin transparent films separating two crystals of identical 

 optical properties (that is like the dark spot of a soap-film), 

 and will therefore in noway interfere with the propagation of 

 light-waves. But with these new conditions we may change 

 the constants of § 1 to the following values in c.G.s. measures 



D = 10- 8 , C = 10 18 xl-8, ^ = 10 " 5 - 



The maximum disturbed curl of a plane-polarized wave in 

 free ?ether with intensity two ergs per cub. cm. will then 

 be e /15 ; in § 1 it was <? /150. 



L. On Surface Separation from Solutions of Saponin, 

 Peptone, and Albumin. By S. A. Shorter, B.Sc* 



THE surface-layers of many solutions contain the dis- 

 solved substance in a degree of concentration much 

 higher than that in the body of the liquid. In some cases 

 the mechanical properties of the surface-layer indicate the 

 separation of matter in the solid state f. The present paper 

 deals with this phenomenon of surface separation in the case 

 of solutions of saponin, peptone, and albumin. The primary 

 object of the investigation was to study the way in which 

 the thickness of the surface pellicle increases with the age 

 of the surface in solutions of various concentrations. Inci- 

 dentally it was found that the results threw much light upon 

 the nature of the molecular processes involved in the forma- 

 tion of the surface-film. It was also found that the results 

 cannot be explained on the ordinary theory of surface 

 concentration. 



In spite of the large amount of work which has been done 

 in recent years on the superficial viscosity and rigidity of 



* Communicated by the Author. Part of the expenses of this research 

 has been defrayed by means of a Government Grant made through the 

 Royal Society. 



f See Ramsden, Proc. Roy. Soc. lxxii. p. 156 (1903). 



