530 Prof. Marianini's Examination of an Experiment 



he should see that the same facts are reproduced which were 

 aU'eady pubHshed by him in 1828, when he wished to found 

 his theory ; and of the many arguments and experiments 

 brought forward by me, he only speaks of two or three 

 secondary in importance, and not with the profundity which 

 one might expect from so distinguished a physicist ! 



In the first part of my said memoir I treat of the influence 

 which voltaic currents exercise in changing the relative electro- 

 motive property of the metals, and of that which is exercised 

 upon them by the liquid conductors, in which are immersed 

 the metals themselves ; and I established some facts which 

 ought to serve as the rationale of some experiments produced 

 by M. de la Rive as inexplicable except upon his theory. 

 But of these we will not speak here. Nor let any one inter- 

 pret this silence into denial or disapprobation, since the same 

 M. de la Rive, in his historical sketch of the principal facts 

 discovered in electricity, makes mention of all these, and not 

 only without starting a doubt of them, but also with expres- 

 sions very flattering to me*. 



In the second part of that memoir I undertake to show the 

 insufficiency of the theory of M. de la Rive to explain the 

 phaenomena of the electromotors, as well simple as complex. 



Treating of the simple electromotors, and of the case in 

 which the two plates are immersed in the same liquid, M. de 

 la Rive adduced in support of his theory that an electric cur- 

 rent is produced when there are immersed in one liquid two 

 portions of the same metal susceptible of being attacked by it. 

 And I observed that if these two portions have some hetero- 

 geneity, the fact accords with the theory of Volta ; if not, there 

 is no theory, either chemical or physical, which can explain 

 it. (Memoir above mentioned, § XXIII.) 



M. de la Rive observed that if a voltaic pair of copper and 

 tin is immersed in an acid or saline solution, the tin is positive; 

 and if it is immersed in ammonia, the copper is positive, because 

 more acted upon by the liquid than the tin. And 1 showed 

 that this second part of the experiment is not true, except 

 after the ammonia may have altered, in a contraiy sense, the 

 electrotism of the two metals, and that, in consequence, it 

 contradicts the theory of M. de la Rive, instead of supporting 

 it. The same observations I made upon the similar experi- 

 ment of M. de la Rive, with copper and iron. (^ XXIV.) 



Another fact which M. de la Rive adduced was, that on 

 immersing iron and lead in concentrated nitric acid, the iron 

 in the first moment is negative, " because (it was said) there 



* Esquisse hutorique des jmncipales dicouvertes fades dans P llectricite 

 depuis quelques armies. Par M. Auguste de la Rive. Geneve, 1833. 



