Capillary and Electrical Phenomena. 287 



tain resemblance to some marine steam-engines. If, now, by 

 means of the binding-screws cr, <r i the whole be connected with a 

 DanielPs element, one mass of mercury is polarized with hydrogen 

 and the other with oxygen. On the first side the capillary con- 

 stant, the capillary depression in and between the tubes, and thus 

 also the force by which the bundle is driven upwards is increased 

 by 035 of its value, and this bundle rises ; exactly the reverse is 

 the case on the other side. The wheel begins to turn ; after a 

 complete excursion, the current is reversed by the commutator 

 and the action begins again in the opposite direction. 



The machine works silently, without sparks, and with very 

 feeble currents, therefore very economically. It once worked 

 five days and nights with a single DanielPs cell. The number 

 of turns, which was 108 in a minute, of course decreases when 

 the sulphate of copper is exhausted*. 



The working-power of such a machine, which is driven by ca- 

 pillary forces, is entirely independent of the volume which it 

 occupies, and depends alone on the variation of the surfaces of 

 contact of the two liquids. This may be readily calculated from 

 the well-known law, that the work of capillary forces is propor- 

 tional to the variation of the surface and is independent of its 

 shape. If, for instance, the E. F. P. of the surface of mercury 

 has successively the values and one Daniell, it may be easily 

 calculated from the numbers above given that the work is equal to 



0*01 x S kilogrammetres, 



if S is the variation of the surface in square metres. 



II. Disengagement of Electricity and Polarization with Capillary 

 Phenomena. 



Experiment has shown that capillary phenomena allow us to 

 transform mechanical work into electrical. Any arrangement 

 which, when a current passes, produces a motion can conversely 

 serve as electromotor. Helmholtz has deduced this reciprocity 

 for electromagnetism and induction from the principle of the 

 conservation of force; his demonstration may without much 

 trouble be put into a somewhat more general form. We have 

 here apparently something similar to induction. 



If, for instance, instead of the battery a galvanometer be con- 

 nected with the electrocapillary engine which has just been 

 described, and the wheel be turned by the hand, it will be seen 

 that the needle deflects ; the deflection continues as long as the 

 turning of the wheel ; the direction of the deflection changes with 

 the direction of the rotation. 



* This machine, as well as the above-named electrometer, is made by M« 

 Jung, mechanician, of Heidelberg. 



