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204 wire. Thus we see that we must have a second wire connected to the negative pole at the home end, and to the first wire at the far end. With one wire alone we can-not transmit electricity from one point in space to another. We must always have two Wires, one outgoing, the other returning. We must, in fact, always have a closed loop. The loop may be quite narrow and many miles long, but it must be a closed circuit. Since the object of sending electricity over a certain distance is not to merely cause a current to flow in the two wires, but to do some useful work at the far end, we must not join the two wires at the far end directly, but must make the connection by way of some apparatus in which the electric current is to be utilised. At one end of our electric line consisting of two wires we have the apparatus which generates electricity, at the other, we have the apparatus which utilises it.

Let the generator at the home end be a dynamo, and the apparatus at the far end a lamp. Since the current in the out-going wire is always exactly of the same strength as that in the incoming wire, there is no accumulation of electricity in the lamp; there is only a conversion of the