400 Mr. S. U. Pickering on the Expansion 



Thus, as a mean, capillary height for clean water is 7*93 

 centim., and for water saturated with camphor 5*64. The 

 ratio of these is *71. 



Observations by myself upon the same tube, but read in a 

 somewhat different manner, gave 



Clean water 804, 8*03, 8'04, 8"05. 



Water changed . . . 8*02, 8*02. 



Camphorated water 5 ; 77, 5*80, 5*79, 5*80, 5*80, 5'83. 



As means we may take 8*03 centim. and 5*80 centim., giving 

 for the ratio '71, as before. 



The ratio of tensions thus found agrees remarkably well 

 with that deduced from the observations upon ripples, viz. 

 •72. It will be remembered that the latter might be expected 

 to be somewhat higher, as corresponding with a condition of 

 things where camphor fragments were nearly, but not quite 

 dead. 



October 8. — I take this opportunity of recording that a film 

 of grease, insufficient to check the motion of camphor frag- 

 ments, exercises a marked influence upon the reflexion of light 

 from the surface of water in the neighbourhood of the polari- 

 zing angle. In the case of a clean surface and at the Brew- 

 sterian angle the reflexion of light polarized perpendicularly 

 to' the plane of incidence appears to vanish in accordance with 

 the formula of Fresnel. 



XLIV. The Expansion of Water and other Liquids. 

 By Spencer Umfreville Pickering, M.A., FM.S* 



[Plates VII. & VIII.] 



MY investigation of various properties of sulphuric acid 

 (Journ. Chem. Soc. 1890, pp. 65, 331, and Phil. Mag. 

 1890, xxix. p. 427) showed that the curved figures representing 

 these properties, or the figures representing the rate of change 

 of these properties with change in percentage composition — 

 the first differential coefficient, obtained by dividing the differ- 

 ence between the values obtained for two different solutions 

 by the difference in their percentage strength — indicated the 

 existence of more or less sudden changes of curvature at 

 certain points corresponding to the composition of definite 

 hydrates. The method adopted in examining any curved 

 figure, to ascertain whether it was a single continuous curve 



* Communicated by the Author. 



