On the fall of Gen. Pelloux he hoped to return to office in a future Sonnino ministry; but as the latter seemed ever less likely to become a reality, Bertolini lost patience and joined Sig.
His conduct in abandoning his old chief was much criticised at the time, but his new patron chose him as Minister of Public Works and Transports in the cabinet of 1907.
He proved a capable administrator, especially when he had to face the nearly total destruction of Messina and Reggio Calabria due to the terrible earthquake of 1908 .
The measure had been introduced to please the demagogic spirit which Giolitti wished to conciliate, but Bertolini must be given credit for the ingeniousness of the machinery which he devised for enabling illiterates to vote and for avoiding electoral corruption as far as possible.
In 1919 Signor Nitti appointed him senator and president of the Italian delegation on the Reparations Commission in Versailles, where he obtained for Italy important compensations from Germany and Austria (which England and France tried to oppose).