718.—All expenses incurred by the Commissioners of Customs in the conduct of suits or prosecutions, or otherwise in carrying into effect the provisions of this Act, shall be considered as expenses having reference to the Revenues of Customs, and shall be paid accordingly; but the Board of Trade may, with the consent of the Treasury, repay out of the Mercantile Marine Fund all or any part of such of the expenses so paid as are under this Act chargeable on that fund.