11. On the requisition of the Magistrate of the district the person in change of a public ferry situate in such district shall maintain at one or more places, in addition to the place at which the said public ferry is established, and within two miles therefrom, such number of subsidiary ferries as may seem to the Magistrate to be necessary for the public convenience: and all the provisions contained in this Act in regard to the management and control of public ferries shall be deemed applicable to any subsidiary ferry maintained under the requisition of the Magistrate.