218 Mr. J. Prideaux on the TJieory of Voltaic Action. 



mical effects. The zinc and silver were in good contact, and 

 so were the zinc and cloth ; but the cloth communicated with 

 the silver only through the points of the tripod, a contact 

 with the liquid insufficient to convey a current capable of any 

 chemical action. 



His third pile was, zinc, tripod, cloth, silver; zinc, tripod, 

 wet cloth, &c. ; and this produced no effects at all. The pile 

 was inert. Yet (as noticed 16.) the communication here was 

 the same as in the previous experiment, except that the tripod 

 intercepted the contact of the zinc with the liquid, instead of 

 that of the silver. But the tripod was of brass, which is nega- 

 tive to zinc, and was in contact with it on one side ; whilst the 

 silver, also negative, was in contact with it on the other. And 

 De Luc attributes the inaction of this pile to the neutralizing 

 effect of the brass and silver on opposite sides of the zinc. 



18. To see how far this explanation, which seemed very 

 probable, would apply, the pair of plates described (14?.) were 

 connected with a multiplier ; the copper placed on the table, 

 a flake of wet paper laid on it, and the zinc plate pressed 

 gently on the paper. 



Deflection ... 30° 

 A slip of sheet copper •*- inch wide, and 3 long, bent into a 

 ring 1 inch diameter, was then placed between the paper and 

 the zinc plate (as in De Luc's third pile). The effect was 

 (as then) null, 0, although greater pressure than before was 

 applied on the zinc. 



A slip of sheet zinc, of similar dimensions to the copper, 

 and similarly bent, was now substituted for it. 

 Deflection ... 27° 

 The paper was now taken up from the copper, and the zinc 

 ring laid on the copper plate ; then wet paper, then the zinc 

 plate. 



Deflection ... 0° 

 The zinc ring was now removed, and the copper one sub- 

 stituted for it, between the paper and the copper plate. 

 Deflection . . . 15° 

 So that interception of the contact between either of the 

 metals and the liquid, by a ring of the electro-opposite metal, 

 entirely intercepts the current. 



19. The action when the wet paper was in full contact with 

 the copper, and only with the ring of zinc, gave deflection 27°. 



When in entire contact with the zinc plate, but only with 

 the ring of copper, 



Deflection . . . 15° 

 15 to 27° deflection being in the proportion of 8 to 19 of 

 electrical current. And this held good (not as to exact pro- 



