ELECTRIC AND MAGNETIC INDUCTIONS IN THE SURROUNDING FIELD, 291 
zinc-acid is greater than V. Then more than V — 1 level surfaces pass between the 
zinc and the acid, the excess over V— 1 going round and passing between the copper 
and the acid, somewhat as in fig. 3, wLere A, B, are the metal plates. The surfaces 
Fig. 3. 
are roughly sketched and numbered, on the supposition that the zinc terminal is at 0, 
the copper at 5, and the acid at 8. They have probably the same shape as those which 
would be produced by condensers at A and B with the wires attached, respectively, to 
one terminal of each, the other terminals being connected together and the charges 
adjusted, so that the difference of potential of the two terminals at A was 3, while that 
at B was 8. 
Fig. 4. 
Let us now suppose the circuit closed. Then the level surface will cut the circuit 
at various points, somewhat as in fig. 4. 
