134 Intelligence and Miscellaneous Articles. 



(2) The use of high potentials so as to drown the polarization 

 E.M.F. 



(3) The use of a balancing cell in a Wheatstone bridge as first 

 suggested by Kohlrausch, employed by Tollinger, and greatly 

 improved by Neesen 



The first method is of very limited application. The third 

 method by itself we know to be quite unsatisfactory, but combined 

 with the first it will be fairly satisfactory as Neesen found. The 

 combination of the methods (2) and (3) which we regard as being 

 the distinguishing feature of our method leaves nothing to be 

 desired, and is in our opinion much more convenient and accurate 

 than the alternating current method. Dr. Neesen makes no claim 

 in his paper of 1884 to have devised a method superior to the 

 alternating current method. 



The last two paragraphs of Dr. Neesen's letter show how little 

 he appreciates the points of our method, one of the main features 

 of which is the employment of high potentials to drown the residual 

 polarization E.M.F. This necessitates high electrolytic resistance, 

 not high resistance of the two equal arms of the bridge. 



1 am, Gentlemen, 



Your obedient servant, 

 W. Stroud. 



SURFACE TENSION OF WATER AND OF DILUTE AQUEOUS 

 SOLUTIONS. BY N. ERNEST DORSEY. 



During the past year I have been endeavouring to determine 

 the surface-tension of dilute aqueous solutions by means of the 

 method of ripples. All work previously done on the surface- 

 tension of solutions has been on solutions of about one half normal 

 concentration, or greater, and most of the observers have deduced 

 the surface-tension from the measured rise of the solution in 

 capillary tubes. 



For at least two reasons the method of capillary tubes is open 

 to serious objections. First, the height a liquid rises in a tube 

 depends upon the angle between the wall of the tube and the 

 surface of the liquid where it meets the tube. This contact angle 

 cannot possibly be measured, since the surface of the liquid lies 

 entirely on one side of the point, where we wish to know its incli- 

 nation ; and as we can measure the inclination of a finite surface 

 only, every measured value of the contact angle must be too large. 



The second objection is that probably the surface-tension of the 

 solution-glass surface, as well as that of the solution-air surface, 

 varies with the concentration of the solution. If such is the case, 

 the surface-tension found will depend upon two changes which 

 cannot be readily separated, and which render the interpretation 

 of the results difficult. 



For these reasons I decided to use the method of ripples, which 

 was first successfully used by Lord Rayleigh, although with his 

 arrangement of apparatus individual observations differ by about 



