Whereas upon that part of the estuary of the Clyde which lies below the jurisdiction of the Trustees of the Clyde Navigation (and which part is in this section referred to as the lower estuary of the Clyde) doubts have arisen as to the limits of the several harbour authorities on that estuary, be it enacted, the F2Secretary of State may, if F2he thinks it expedient, make byelaws under this Act for the lower estuary of the Clyde as if it were a harbour and F2he were the harbour authority, and such byelaws shall be deemed to have been made by a harbour authority with the sanction of the F2Secretary of State ; and F2he may by such byelaws define the area within which such byelaws are to be observed, and the Secretary of State shall have power to define the authority or authorities and officers by whom such byelaws are to be enforced and carried into effect within such area; and such authority or authorities and officers shall, for the purposes of this Act, other than making byelaws or assenting to a site for a new factory or magazine, have the same power within the said area as a harbour authority and an officer of a harbour authority have respectively under this Act in a harbour.