COMPOUND VOLTAIC CIRCLE. 



213 



Zincl 



FIG. 15. znic plates, both supposed to be in 



contact with hydrochloric acid, namely 

 at A and at C, and a copper plate 

 attached to each of these zincs. The 

 circle is made up of two pairs of 

 copper and zinc, copper and zinc, 

 w jth ac id between each pair. The 

 polar condition of such a circle will 

 easily be observed. By the contact 

 of the acid and zinc at A, a zincous pole is established there 

 in the first zinc plate, and a chlorous pole in the acid, which 

 are so inscribed in the diagram. These occasion the for- 

 mation of a chlorous pole at D in the first copper, the united 

 zinc and copper A D forming together one polar element ; 

 and a zincous pole at B in the acid, the column A B of 

 acid, being the second polar element. The further effect 

 of the induction is to produce a chlorous pole at B in the se- 

 cond copper, of which the corresponding zincous pole is at C, 

 in the second zinc ; the united zinc and copper B C forming 

 together a third polar element. And, as a last consequence 

 of the inducing force originating at A the column of acid 

 between C and D becomes a fourth polar element of the 

 circle, having a chlorous pole at C and a zincous pole at D. 

 Now it will be observed that the chemical affinity between 

 the acid and zinc at C tends to produce the same polar con- 

 ditions at that point, as are already established there from 

 the effect of induction. The extremity of the zinc plate at 

 C is in fact zincous both primarily and by induction ; and 

 the acid in contact with it, likewise chlorous, both primarily 

 and by induction ; and generally throughout the whole circle, 

 the polar conditions determined by the second chemical action 

 at C are the same as those determined by the first action at A. 

 FIG. 1 6. In the last arrangement, the in- 



Fluid ductive actions are in the same direc- 



tion, and favour each other ; but a 

 circle may be constructed in which 

 the inductions, being in opposite 

 er directions, oppose and neutralize 

 each other. Thus if A D (Fig. 1 6.) 

 be entirely zinc, both its extremities 

 Fluici being exposed to acid, will tend 



