The Earth an Important Part of a Telegraphic System
Modern Electrical Inventions
We learned that electricity could flow through many different substances, one of which was the earth. In all ordinary telegraph lines, advantage is taken of this fact to utilize the earth as a conductor and to dispense with one wire. Originally two wires were used; then it was found that a railroad track could be substituted for one wire, and later that the earth itself served equally well for a return wire. The present arrangement is shown in Figure, where there is but one wire, the circuit being completed by the earth. No fact in electricity seems more marvelous than that the thousands of messages flashing along the wires overhead are likewise traveling through the ground beneath. If it were not for this use of the earth as an unfailing conductor, the network of overhead wires in our city streets would be even more complex than it now is.
FIG. - Diagram of a modern telegraph system.