Gramme's motor; "discovery" of DC motor

The Belgian scientist, Zénobe Gramme (1826-1901), developed a commercial DC generator in 1871. This is shown below; the horse-shoe-shaped electromagnetic is the stator, and the rotor that carries a toroidal coil is rotated to generate electricity. In 1873, when Gramme exhibited two of these generators at the International Exhibition in Vienna, his partner accidentally connected the output cables of one machine to those of the other machine. When one generator was started up, the other machine began to rotate. Thus, it was discovered that a DC generator can also be used as a DC motor.