In February 1888 Galileo Ferraris presented to the Royal Academy of Sciences of Turin his research on the rotating magnetic field: the physical principle that allows an alternating-current induction motor to spin without physical contact between stator and rotor. It is the technical basis of the modern AC motor. Three months later, Nikola Tesla filed his patent for the AC polyphase system in the US. Both apparently reached the same principle independently; Ferraris did not patent it and declared the system commercially unviable, leaving the field open for Tesla and Westinghouse. In the long history of electrification, Ferraris is one of the great unpatented originators: technically first, historiographically second.