Electrical Igniter for Gas EnginesGasoline-powered engines were also very new in the late 1800s. In this patent for an Electrical Igniter for Gas Engines, Tesla proposes to use the piston of the engine as one terminal of an electric circuit and the base of the cylinder as the other. If enough charge is built up in the piston, the charge will jump to a point at the base of the cylinder causing a spark. This spark will ignite the gasoline.
Image courtesy of Tesla Universe