lletardation produced by interposed Plates. 347 



few minutes the current almost entirely ceased. Tliis effect 

 appears due to the surfaces taking up that peculiar condition 

 (1040.) by which they tend to produce a reverse current; for 

 when one or more of the plates were turned round, which 

 could easily be effected with the couronne des tasses form of 

 experiment, fig. 18, then the current was powerfully renewed 

 for a few moments, and then again ceased. Plates of platina 

 and copper, arranged as a voltaic pile with dilute sulphuric 

 acid, could not form a voltaic trough competent to act for 

 more than a few minutes, because of this peculiar counteract- 

 ing effect. 



1031. All these effects of retardation, exhibited by decom- 

 position against surfaces for which the evolved elements have 

 more or less affinity, or are altogether deficient in attraction, 

 show generally, though beautifully, the chemical relations and 

 source of the current, and also the balanced state of the affi- 

 nities at the places of excitation and decomposition. In this 

 way they add to the mass of evidence in favour of the identity 

 of the two ; for they demonstrate, as it were, the antagonism 

 of the chemical powers at the electromotive part with the che- 

 mical powers at the interposed parts ; they show that the first 

 are producing electric effects, and the second opposing them ; 

 they bring the two into direct relation ; they prove that either 

 can determine the other, thus making what appears to be 

 cause and effect convertible, and thereby demonstrating that 

 both chemical and electrical action are merely two exhibitions 

 of one single agent or power (916. &c.). 



1032. It is quite evident that as water and other electro- 

 lytes can conduct electricity without suffering decomposition 

 (986.), when the electricity is of sufficiently low intensity, it 

 may not be asserted as absolutely true in all cases, that when- 

 ever electricity passes through an electrolyte, it produces a 

 definite effect of decomposition. But the quantity of electric 

 city which can pass in a given time through an electrolyte 

 without causing decomposition, is so small as to bear no com- 

 parison to that required in a case of very moderate decompo- 

 sition : and with electricity above the intensity required for 

 decomposition, I have found no sensible departure as yet from 

 the law of definite electrolytic action developed in the preced- 

 ing series of these Researches (783. &c.). 



1033. I cannot dismiss this division of the present paper 

 without making a reference to the important experiments of 

 M. Aug. De la Rive on the effects of interposed plates *. As 

 I have had occasion to consider such plates merely as giving^ 



* Annates de Chimie [et de Physique^, iom. xxviii. p. 190; and Memoires 

 de Geneve, 



2 V2 



