230 Mr. H. J. Chaney. Re-determination of the [June 19. 



The outside of the bulb was silvered, observations taken, and the 

 silver then dissolved without touching the suspension, and observations 

 again taken. 



Silvered surface . . 9'898 sec. log. dec. O20718 



Glass .. 9-938 0'20751 



Ratio of frictions 1 : 1 '00564. 



The change is thus less than 0'6 per cent., and is within the limits of 

 experimental error. 



The main part of Helmholtz's paper is taken up with the con- 

 sideration of experiments on the oscillations of an accurately worked 

 sphere. It is remarkable that he deduces a value for the coefficient 

 of viscosity which is about a quarter greater than that given by 

 Poiseuille. This seems to suggest that a slight change in the applica- 

 tion of theory to the results of experiment is needed, which will 

 reduce the coefficient for the viscosity of the liquid, and increase the 

 value for its adhesion to the walls of the vessel to that required for 

 the condition of no slip. The existence of any effect approaching in 

 magnitude that given by Helmholtz would produce, as I have shown, 

 such an enormous change in the time of flow through a silvered tube, 

 that the result of my experiments must be considered quite conclusive. 

 The argument from the differences in friction due to differences in 

 surface, in favour of the contact theory of E.M.F. is now seen to be 

 worthless ; and it must be admitted that no slip occurs, at any rate 

 with solids that are wetted by the liquid. 



III. "Re-determination of the True Weight of a Cubic Inch of 

 Distilled Water." By H. J. CHANEY. Communicated by 

 the President. Received February 4, 1890. 



(Abstract.) 



Recent investigations as to the value of the metric unit of volume 

 the cubic decimetre appear to show, indirectly, that the present 

 weight of a cubic inch of distilled water (252'458 grains, t = 62 F., 

 J) = 30 in.) the hitherto accepted unit of volume in this country 

 is appreciably too high. This weight (252'458 grains) is based on 

 weighings made by Shuckburgh in 1798, and on linear measurements 

 by Kater in 1821 ; but their results are affected by uncertainty as to 

 thermometric and linear measurements, and as to the condition of the 

 water used. Hence a direct re-determination of the unit of yolume 

 in this country appeared now to be desirable. 



