The Guardians may from Time to Time provide such a Fund, to be called “The Reserve Fund,” as in their Opinion will be sufficient to rebuild or restore the Birmingham Proof House, and every Branch Proof House of the Guardians, and the Works and Conveniences thereof respectively, in the event of the same being destroyed or damaged by Fire, Explosion, or other Casualty, and to make good all Damage which the Guardians may be liable to compensate by reason of such Casualty, and may from Time to Time invest that Fund in some of the Public Funds or in Government Securities, or on Mortgage of Freehold Securities, or of any City, Borough, or other Municipal Rates or Funds, in the Name of the Guardians of the Birmingham Proof House, and until so invested may deposit the same in any Bank, and, when necessary, convert the same or a Part thereof into Money, and apply the Proceeds thereof for the Purposes mentioned in this Provision: Provided always, that the Investments and Monies at the Commencement of this Act representing the Repair Fund under the recited Act shall be deemed Part of the Reserve Fund under this Act.