  A recently proposed method of continuous unitary transformations is used to
eliminate the interaction between electrons and phonons. The differential
equations for the couplings represent an infinitesimal formulation of a
sequence of Fr\"ohlich-transformations. The two approaches are compared. Our
result will turn out to be less singular than Fr\"ohlich's. Furthermore the
interaction between electrons belonging to a Cooper-pair will always be
attractive in our approach. Even in the case where Fr\"ohlich's transformation
is not defined (Fr\"ohlich actually excluded these regions from the
transformation), we obtain an elimination of the electron-phonon interaction.
This is due to a sufficiently slow change of the phonon energies as a function
of the flow parameter.
