﻿188 Mr. William Sutherland on the 



Bjerknes has shown* that the oscillations in a Hertz 

 resonator are not damped out so quickly as those in the pri- 

 mary exciting circuit. My photographs also show that the 

 oscillations in all neighbouring circuits continue long after 

 the unidirectional spark in the primary or exciting circuit has 

 ceased. This is true whether there is resonance or not, and 

 is more marked when the circuits are not in tune, except so 

 far as electrical beats tend to damp the oscillations of the 

 secondary circuit. 



I am inclined to believe, therefore, that the conclusions of 

 Bjerknes are true only for open circuits or circuits in which 

 no sparks occur. When sparks occur in two circuits which 

 are in resonance the duration of time-sparks appears to be 

 the same. With periods ranging from '00001 to '000001 of 

 a second, I have found it impossible to tune two circuits in 

 which sparks occurred to perfect resonance. There were 

 always indications of beats due, I believe, to the capacity not 

 rising immediately to its full value. 



The method which I have outlined in this paper seems to 

 offer a fruitful one for investigation ; for a large number 

 of comparative photographs can be taken with far greater 

 ease than by the arrangement of apparatus employed by 

 Feddersen. 

 Jefferson Physical Laboratory, 



Harvard University, Cambridge, Mass., U.S. 



XX. The Attraction of Unlike Molecules. — II. TJie Surf ace- 

 Tension of Mixed Liquids. By William Sutherland!. 



THE most direct method of measuring the attractions of 

 unlike molecules seems to be by obtaining a theoretical 

 expression for the surface-tension of mixed liquids involving 

 the attractions of the unlike molecules of the liquids as well as 

 the attractions of the like molecules for one another, and then 

 by experimental determinations of the surface-tensions of 

 mixtures to obtain the data wherewith to calculate the attrac- 

 tions of the unlike molecules from the theoretical expression. 

 The present paper contains both a theoretical and an experi- 

 mental part, of which the theoretical had better come first as 

 indicating the lines on which the experiments are to be 

 discussed. 



In a paper on the Law of Molecular Force (Phil. Mag. 

 [5] vol. xxvii. p. 305), which has been largely superseded by 



* Ann. dei' Physih und Chemie, xliv. 1891 ; xlvii. 1892. 

 t Communicated by the Author. 



