332 Mr. G. J. Burch. On Professor Hermanns 



Hermann has passed over C, and omitted to take W into account, 

 confining himself to the theoretical relation between Q* and P/. 



But we know very little about polarisation, save in the case of 

 solid electrodes. The term polarisation, as frequently used, includes 

 two phenomena, which ought to be kept distinct, viz. : 



(a) That condition of the interface between two conductors, of 

 which one at least is an electrolyte, in which the molecules are under 

 a stress not greater than they are capable of supporting without 

 chemical change. . 



(&) A deposit upon the surface of a solid, or in the contiguous 

 liquid, of the products of actual electrolysis. 



If one of the conductors is a solid, the inevitable local differences 

 of condition or of composition enable actual electrolysis to take 

 place, even with a P.O. smaller than that proper to the chemical 

 change implied. 



But if both conductors are liquid and perfectly pure, the stress is 

 so far equalised that no electrolysis is possible until the E.M.F. 

 reaches a certain value, more sharply defined in proportion as the 

 materials are pure. 



I hold that with differences of potential which do not reach this 

 limit, the electromotive force is transmuted without electrolysis into 

 mechanical force, and manifests itself as kinetic energy, until by the 

 motion of the meniscus it becomes transformed into potential energy. 



The locus of transformation from electrical to mechanical force must 

 clearly be the two interfaces mercury-acid and acid-mercury, and it 

 is upon these that the stress acts. The resistance is distributed along 

 the tube, and is partly electrical, but to a far larger extent mecha- 

 nical. 



Is it reasonable, therefore, to assume that the sole cause of delay 

 is the " Polarisations-geschwindigkeit " of the meniscus ? 



I believe that in the case of an interface between two liquids, the 

 rate of polarisation is to be measured in terms of the vibration-period 

 of a molecule, rather than in decimals of a second. 



Actual electrolysis is another matter, and I hold that it does not 

 take place in a properly working electrometer. We do not assume 

 electrolysis when two pith balls repel each other after receiving a 

 charge, nor when a closed coil is slipped over a magnet. But the 

 coil cannot be got off again, nor can the balls fall together without 

 the generation somewhere of a current. , I cannot see why we should 

 assume electrolysis in the case of the capillary electrometer. The 

 marvellous rapidity of the action to which I have not yet found a 

 limit, is against it, as is also the fact that the substitution for the 

 acid, or the addition to it, of any substance which can be electrolysed 

 by a smaller electromotive force, reduces the range of potential dif- 

 ference for which it can be used. 



