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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1892 Excerpt: ...such reversibility in a conduction current. The case is, of course, substantially the same as in charging a condenser, the difference being in the amount of capacity and the quantity of electricity concerned, which are excessively small when the terminals have no large opposed surfaces connected to them. And the same thing occurs when the circuit is closed conductively, there being also other circuits through the air on starting the current, which results in charging the wire. The observed difference of potential of the disconnected cell should not be confounded with its E.M.F. They are numerically equal, but opposed in direction, as regards their power of producing current in the circuit, viz., cell and air. That this is so is evident on considering that if there were no E.m.f. to keep up the static charges they would unite through the cell itself. It is the same when we have not an ordinary galvanic cell, but merely two metals A and B in contact in air, forming a circuit A, air, B, A. If we find B at a higher potential than A, the E M.F. that caused it must have been numerically equal to their difference of potential, and have acted in the direction B, air, A, B, with a transfer of electricity in this direction round the circuit, lasting until the difference of potential stops further current. It is no easy matter, however, to settle exactly where the small consumption of energy needed for this state of electrostatic energy comes from, though frobably it arises merely from a very minute amount of chemical action. See Section XIII. later. Since EQ of work is done by E during the passage of Q, an amount EC is done per second. The supply of energy obviously comes from the galvanic cell, of which more later, whilst we now consider its destination. In W = EQ i...

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