On the Nature of Electro-capillary Phenomena. 25."> 



Gum-canals abundant in the petioles and leaf-bases, and in the cor- 

 tex, and around the steles of the stem. 



Adventitious roots borne in vertical series, triarch, with secondary 

 wood and bast, and periderm. 



Stem with leaf-bases, about 7 8 cm. in mean diameter. 



Petioles about 2 '5 4 cm. in diameter at base, diminishing to about 

 1 mm. in the ultimate branches of the rachis. 



Leaflets about 3 mm. wide. 



Roots reaching 12 mm. in diameter. 



Locality : Hough Hill Colliery, Stalybridge, Lancashire. 



Horizon : Low^er Coal-measures. 



Found by Messrs. G. Wild and J. Lomax, 1892-98. 



" On the Nature of Electro-capillary Phenomena. I. Their Rela- 

 tion to the Potential Differences between Solutions." By 

 S. W. J. SMITH, M.A., formerly Coutts-Trotter Student of 

 Trinity College, Cambridge ; Demonstrator of Physics in the 

 Eoyal College of Science, London. Communicated by Pro- 

 fessor A. W. RUCKEB, Sec. RS. Received January 5, Read 

 January 26, 1899. 



(Abstract.) 



1. The Lippmann-Helmholtz theory of the capillary electrometer 

 contains two assumptions. 



2. The first assumption would apply to any electrolytic cell. A 

 deduction from it, which would apply to any cell having a large and a 

 small electrode, is that the variation of the potential difference at the 

 capillary electrode of an electrometer is the same, as that of the applied 

 electromotive force. 



In order to trace the relation between surface tension and potential 

 difference on the view that this first assumption is correct, it is neces- 

 sary to eliminate the possible effect of depolarisation upon the form of 

 the electro-capillary curve i.e., the curve which shows the relation 

 between the surface tension and the applied electromotive force. A 

 direct method of examining the depolarisation current is described and 

 applied. An estimate of the magnitude of the depolarisation effect is 

 given, and the circumstances under which the effect may become 

 appreciable are discussed. 



3. The second assumption of the Lippmann-Helmholtz theory, that 

 the electro-capillary phenomena are controlled by a simple variation 

 of the electrostatic surface energy, leads to two conclusions, each of 

 which is beset with difficulties. 



