334 HERMANN VON HELMHOLTZ 



that the curvature was greatest at the vertex. The experi- 

 mental series coincided in showing that the surface-tension 

 reaches a maximum at a moderate degree of polarization, 

 which differs for different fluids. Helmholtz now assumed that 

 the forces under the influence of which equilibrium is produced 

 at the polarized surface, between the molecular and electrical 

 forces acting at the summit of the drop, are conservative, and 

 finds on this assumption that there is no difference of potential 

 between the mercury and the fluid in the state of maximal 

 surface-tension, and that the surface presents no trace of an 

 electrical double layer. In conclusion he showed further, by 

 using the mercury as an electrode, that Faraday's electrolytic 

 law, by which, where no electrolysis is possible, there can be 

 no transference of electricity from the metal to the electrolytes, 

 or vice versa, is only in apparent contradiction with the ex- 

 periments on the galvanic currents that can be excited by the 

 successive immersion of two similar electrodes in the same fluid. 



The year 1882 brought high honour and distinction to Helm- 

 holtz and his family : he was elevated by the Emperor William I 

 to the ranks of the hereditary nobility. The appearance of 

 Vol. I of his Wissenschaftliche Abhandlungen ( l Scientific 

 Papers'), followed in the next year by a second volume, had 

 brought the astonishing extent of his great scientific achieve- 

 ments before the eyes of the world. 



A year of hard work brought him to the conclusion of his 

 profound investigations in thermodynamics, and these at once 

 formed the starting-point of his remarkable theory of the 

 statics of monocyclic systems, culminating eventually in the 

 fundamental researches into the principle of least action with 

 which he was occupied to the end of his life. On September 

 18, 1882, he writes to Thomson : 



'After ten months of work I was longing for undisturbed 

 rest, for which I always find Pontresina one of the best places 

 in the world. On October 16 I have to go to Paris as a Member 

 of the International Commission of the Electrical Congress. 

 My Faraday Lecture put me on to electrical researches : I 

 hope you have received my first note on this subject, " On the 

 Thermodynamic Value of Chemical Actions." A second has 

 just been published, a comparison of the chemical energy 

 of solutions, &c.' 



