Connexion between Capillary and Electrical Phenomena. 281 



In concluding these remarks, I take occasion to advert to the 

 solution I have given, on hydrodynamical principles, of the 

 problem of lines of magnetic force, this problem being in its 

 conditions analogous to that of determining the effect of the 

 small globules of water in a foggy atmosphere on the intensity 

 of sound. (See the " Note on the Hydrodynamical Theory of 

 Magnetism" in the Philosophical Magazine for July 1869, 

 pp. 42-45, and arts. 4-8 of a new discussion of the same 

 theory in the Number for June 1872). In that solution I have 

 argued that a stream, or a vibration, of the sether receives an 

 impulse on entering into a magnet by reason of the contraction 

 of channel resulting from the occupation of space by the atoms 

 of the magnet, and that this impulse is proportional to the 

 number of atoms in a given space. On the hypothesis, there- 

 fore, that the density of the magnet increases by slow degrees 

 from one end to the other, a given element of the aether will 

 receive successive impulses as it moves towards the denser end, 

 and in this way a permanent stream will be maintained in oppo- 

 sition to the inertia of the fluid. In the case of the transmission 

 of sound in a foggy atmosphere, there is not an analogous incre- 

 ment of the globule-density in the horizontal direction of the 

 propagation; but so far as experiment indicates that an im- 

 pulse is given to the sound-vibrations by the presence of the 

 globules and the intensity of the sound is thereby increased, 

 the two kinds of phenomena are alike, and the proposed theore- 

 tical explanations of them are mutually confirmatory. 



Cambridge, March 18, 1874. 



XXXIV. Connexion between Capillary and Electrical Phenomena, 



By Gabriel Lippmann*. 



[With a Plate.] 



THE present investigation was made in the laboratory of 

 Professor Kirchhoff, to whom I am greatly indebted for 

 his counsel and for his kind assistance. It might well have been 

 difficult to seek a priori for relations between electrical variables 

 and the so-called constants of capillarity ; and in fact I only 

 gradually arrived at such relations, starting from an experiment 

 for which I am indebted to Professor Kuhne of Heidelberg, and 

 which is essentially as follows. 



A drop of mercury is introduced into dilute sulphuric acid in 

 which is dissolved a trace of bichromate of potash ; a polished 



* Translated from Poggendorff's Annalen, vol. cxlix. p. 546. 



[Note. — In a paper by Mr. C. F. Varley, read before the Royal Society, 

 January 12, 1871, and published in this Journal, vol. xli. p. 310, some of 

 the results contained in thispaper have been anticipated. — Ed. Phil. Mag.] 



