Early Leakage Currents
The telegraph system, which performed
remarkably well over long distances in the arid American west, was greatly limited
in distance when installed on the humid east coast. Leakage currents through the
water-impregnated wire insulation greatly attenuated the signals, especially when
buried underground. To cure the problem, Sir William Thompson invented gutta-percha
insulation, and in 1847 designed a screw-press for coating the wires with the gum
rendered plastic by heat.