After having obtained his degree, Mossotti stayed two more years in the
University of Pavia with the qualification of ``auditor", which was similar to
a research assistant, a sort of apprenticeship to become a lecturer and a
researcher. He helped Brunacci with his research, as testified by Mossotti's
first published work in 1813, a note about a problem on the theory of the
hydraulic ram
. In his note, Mossotti solved the fundamental
problems of the theory of the hydraulic ram with the aid of the principle of
virtual velocities.