Early Leakage Currents
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.