What experience served as the basis for M. Faraday to hypothesize the existence of the phenomenon

What experience served as the basis for M. Faraday to hypothesize the existence of the phenomenon of electromagnetic induction?

In 1831, Faraday conducted an experiment that allowed him to define a phenomenon he called “electromagnetic induction”. The essence of the experiment was as follows: Two coils wound on a wooden frame were located close enough. A galvanometer was connected to one coil, while the second was connected to a battery. When the second coil was connected to the battery, the galvanometer showed the presence of a weak current in the first coil. A similar current was observed when the second coil was disconnected from the battery.