260 Dr. S. A. Shorter on the Constitution 



Thus the transmission through the crystal had not pro- 

 duced a deflexion of *012 millimetre at a distance of 140 

 (about) centimetres from the refracting prism ; that is, the 

 deviation was less than 2 seconds of arc. We conclude 

 from this that the refractive index of potassium bromide for 

 radiation of wave-length in the neighbourhood of '5 x 10 " 8 cm. 

 is between 0'999995 and 1-000005 *. 



It is of course possible that if only radiation of frequency 

 within certain narrow limits were refracted appreciably, the 

 intensity of this would be too small to produce a distinguish- 

 able feature on the photographic plate. 



Experiments with more nearly homogeneous beams of 

 radiation might indicate such refraction for a particular 

 wave-length. Although this is a possibility, there is little 

 reason for expecting that such experiments would lead 

 to results differing from those already obtained. Eor the 

 radiations used in these experiments covered a great portion 

 of what may be regarded as the K absorption band associated 

 with the bromine "K" radiation. 



I wish to express my thanks to Mr. J. H. Hagger, — 

 now Inspector of Munitions — for his assistance in these 

 experiments. 



XXXIII. On the Constitution of the Surface Layers of 

 Liquids. By S. A. Shorter, D.Sc, Assistant Lecturer 

 in Physics in the University of Leeds. — Part I. f 



Contents. 

 § 1. Introduction. 



§ 2. The General Case of a Binary System. 

 § 3. The Principle of the Relativity of the Surface Magnitudes. 

 § 4. Special Cases of a Binary System. 



§ 1. Introduction. 



THE principles of thermodynamics were first applied to 

 the question of the constitution of the heterogeneous 

 layer separating two phases, by Gribbs in his well-known 

 work " On the Equilibrium of Heterogeneous Substances " %. 

 As in the case of many other extremely interesting problems, 

 Gibbs's mode of treatment of the subject presents mathe- 

 matical difficulties, which are insuperable to practically all 

 of those to whom the subject is of interest. The object of 



t Communicated by the Author. 

 }' Scientific Papers, vol. i. p. 235. 



