How electrolysis may occur in a trolley system. TT is the trolley wire, RR is the track. As shown by the arrows, the regular flow of the current should return to the rails. If there is a pipe LL that offers a steady current, it will cause the current to leave the rails (I), enter the pipe, and flow out (0). P is the powerhouse that powers the wire and trolley (C).
International Correspondence Schools A Textbook on Electric Lighting and Railways (Scranton, PA: International Textbook Company, 1901)