212 INDUCTIVE AFFINITY. 



four segments, or has four polarized elements, every terminal 

 pole of which is in contact with a pole of a different name ; 

 and the whole arrangement may be compared to a circle of four 

 magnets with the attractive poles in contact. 



FIG. 14. These elements are : 



First, the zinc plate or po- 

 sitive metal, A L, of which 

 the end at A, in the hydro- 

 l| C ne P g S r chloric acid (Fig. 14.), has 

 metal j^j metal zincous affinity, and the 



end at L., in the hydri- 

 odic acid, chlorous affi- 



nit y- 



Secondly, the body of hydrochloric acid, A F, between the 

 zinc and copper plates, of which the surface at A, in contact 

 with the positive metal, has chlorous, and that at F in contact 

 with the negative metal, zincous affinity. 



Thirdly, the copper or negative metal F K, of which the end 

 at F in the hydrochloric acid, has chlorous affinity, and at K, in 

 the hydriodic acid, zincous affinity. 



And fourthly, the body of hydriodic acid, K L, between the 

 zincous and chlorous poles of the negative and positive metals, 

 of which the surface K, in contact with the negative metal, is 

 chlorous, and the surface L, in contact with the positive metal, 

 zincous. 



In every voltaic circle employed to produce decomposition, 

 these four elements are to be looked for. Hereafter, in ad- 

 verting to any one of these elements it will be sufficient to confine 

 our notice to its terminal polarities or affinities, without re- 

 curring to the polarized condition of the element itself, upon 

 which its terminal affinities depend. 



COMPOUND VOLTAIC CIRCLE. 



In both the arrangements described there is only one source 

 of polarizing force, namely the action between the zinc and 

 acid at A. But a circle of a similar nature may be constructed 

 embracing within itself two or more of such primary sources 

 of polarizing power, and the intensity of the polar condition of 

 the whole circle be thereby greatly increased. 



Figure 15 represents such a circle in which there are two 



