After the channel of the Crum River where the same empties into the Delaware River has been changed, diverted, and straightened under the authority given to Alba B. Johnson and Samuel M. Vauclain and the Baldwin Locomotive Works by Act July 27, 1916, chapter 260, the said Crum River, as so straightened, shall be a public navigable stream, and the course and channel of the said river, as it existed July 27, 1916, from the right-of-way of the Philadelphia and Reading Railway Company to the low-water line in the Delaware River shall be abandoned and vacated when the above-mentioned new channel shall have been completed to a depth of four feet at mean low water, with a bottom width of sixty-two feet and width of one hundred feet at mean low-water level: Provided, That the Government shall have such right, title, and interest in and to the bed of said new channel as will assure the public the right to the perpetual use of said channel for all the purposes of navigation and commerce.