For the purpose of defraying any expenses chargeable on the district fund which that fund is insufficient to meet, the urban authority shall from time to time, as occasion may require, make by writing under their common seal, and levy in addition to any other rate leviable by them under this Act, a rate or rates to be called " general district rates."
Any such rate may be made and levied either prospectively in order to raise money for the payment of future charges and expenses, or retrospectively in order to raise money for the payment of charges and expenses incurred at any time within six months before the making of the rate in calculating the period of six months during which the rate may be made retrospectively, the time during which any appeal or other proceeding relating to such rate is pending shall be excluded.
Public notice of intention to make any such rate, and of the time when it is intended to make the same, and of the place where a statement of the proposed rate is deposited for inspection, shall be given by the urban authority in the week immediately before the day on which the rate is intended to be made, and at least seven days previously thereto ; but in, case of proceedings to levy or recover any rate it shall not be necessary to prove that such notice was given.