arfrfMc^rf^j/ Prof. Faraday m5M^/3or^o/"De la Rive's Theory. 199 



ductibility of the apparatus, an increase observed and noted 

 by M. de la Rive, and by myself many years ago *, the ex- 

 planation of the phaenomenon will become easy and natural; 

 and whoever wishes to see this verified has only to repeat the 

 experiment, which I now proceed to describe. 



Having plunged a voltaic pair into two cups of acidulated 

 water, as in the experiment of the preceding paragraph, I put 

 the liquid of the cup in which the copper was plunged in 

 communication with a third cup, containing some of the same 

 liquid, by means of an arc formed by a plate of copper; and 

 in this cup was plunged another plate of copper, which formed 

 one of the extremities of the galvanometric wire ; whilst the 

 other was dipped, by means of a plate of copper, into the cup 

 containing the zinc plate of the pair. All being thus arranged, 

 I closed the circuit, and the needle deviated nearly to the 

 fortieth degree, and then stopped at the eighth ; and after a 

 minute, I interrupted the circuit and held it open for half a 

 minute; after which time the needle was stationary at zero, 

 and having completed the circuit again the needle deviated 

 quickly to thirty degrees, and then stopped again at the eighth 

 degree. Hitherto the liquid was not agitated ; but a minute 

 after the needle became stationary, I opened the circuit, I 

 stirred the liquid in the third additional cup, that namely, in 

 which was plunged one end of the arc of copper joined to the 

 pair, and one plate of copper attached to one end of the wire 

 of the galvanometer, and after half a minute, the circuit being 

 completed, the needle deviated to the thirty-fifth degree, and 

 stopped afterwards upon the ninth. 



If instead of stirring the liquid the plates immersed in it 

 are slightly touched with a feather, the increase of strength is 

 observed without interrupting the circuit. In one of the ex- 

 periments made in this manner, the needle was stationary at 

 the sixth degree, and after brushing the plate of copper an- 

 nexed to one end of the galvanometric wire and immersed in 

 the third cup, the needle moved to nine degrees, whence it 

 turned quickly to six. The same thing happened upon brush- 

 ing gently the plate which served as an arc in the part im- 

 mersed in the cup containing the zinc plate of the pair. 



Now in such experiments those plates of copper served only 

 to convey the electricity put in motion by the voltaic pair ; 

 then the agitation of the liquid or that light friction upon the 

 plates of copper, strengthens the current in proportion as the 

 power of conducting or transmitting the electricity is streno-th- 

 ened in the apparatus. " 



" Memoir upon the loss of tension which electromotors undergo, &c. 

 Section 15.— A?inales de C/iimic et dc Phytique, August, 1828, 



