13.—The sum of £1,000,000, being the total of repayable advances to the Board for capital expenditure which, having been included in a Supplementary Estimate approved by Dáil Éireann on the 25th day of July, 1956, were granted by the Central Fund Act, 1957, and appropriated for that purpose by the Appropriation Act, 1957, shall be treated as a non-repayable grant from the 1st day of April, 1958.