a Conducting' Liquid electrified in Mercury. 195 



•mediate and necessary consequences of the physical law there 

 established. 



In the professor's first experiment, a plate of iron, suspend- 

 ed horizontally to one arm of a balance, was brought in con- 

 tact with water, and its adhesion just balanced by weights in 

 a scale attached to the other arm. The water being connect- 

 ed with one pole of a galvanic pile, and the plate and balance 

 with the other, the equilibrium remained undisturbed. But 

 when the plate was placed in contact with a thin stratum of 

 water covering mercury, on connecting one pole with the mer- 

 cury, anil the other as before with the balance, the equili- 

 brium was immediately destroyed, and the plate descended 

 with a jerk. This effect he attributed to increased cohesive 

 attraction, but its true cause must be looked for in the sudden 

 displacement of the water by the radiating currents produced 

 in the mercury — in the manner described in my paper, the 

 rush downwards from the plate to supply the void, the set of 

 the surrounding liquid inwards, and the pressure of the atmo- 

 sphere, which forces down the plate into the vacuum left un- 

 supplied from the sources just enumerated. 



Another experiment described by Professor Erman is as 

 follows : A globule of water dropped on the surface of a flat 

 dish of mercury is brought into connexion with the positive 

 pole, while the mercury is connected with the negative. It 

 instantly flattens, and spreads to twice its diameter, regaining 

 its former sphericity when the circuit is broken. On this he 

 remarks, that " the same act which has imparted to the quick- 

 silver a decomposing affinity for the water, has at the same 

 time, or previously, effected an increased cohesive attraction 

 between these two fluids." In this view of the case, the ex- 

 tension of the drop on the quicksilver is purely a statical re- 

 sult, tli3 molecules assuming their position of equilibrium un- 

 der the new circumstances of capillary action in which they 

 are placed. In my paper, the same phenomenon is described, 

 and is attributed, if I mistake not, to its true immediate cause, 

 viz. a radiation of the superficial molecules of the mercury in 

 all directions from the points nearest the positive pole as a 

 centre, dragging with them the fluid particles adjacent, and 

 thus diffusing them over a larger surface. In this view, the 



