In subsection (1) of section seven of the [(1 Edw. 8 and 1 Geo. 6. c. 28).] Harbours, Piers and Ferries (Scotland) Act, 1937 (which provides that in certain circumstances the Secretary of State may authorise a local or harbour authority to undertake, subject to the Second Schedule to the said Act, certain operations in connection with a marine work) for the words " five thousand pounds " there shall be substituted the words " twenty-five thousand pounds ".