Gian Domenico Romagnosi’s Forgotten Experiment on the Magnetic Effect of Currents in 1802

We briefly investigate an experiment carried out by Gian Domenico Romagnosi, in 1802, and concerning the deviation of a compass needle due to galvanic flow, indeed, cited by Ørsted himself, universally acknowledged as the discoverer of this phenomenon, in 1820, and try to understand why the former is unknown even to most of the specialists.