If any intending purchaser, other than the holder of the run, shall apply to the Commissioner to purchase land forming a Run or portion of a run which is with the sanction of Government in the bona fide possession of such holder; which shall in the opinion of such Commissioner be sufficiently stocked; and which, upon the application of the holder of the run to such Commissioner, shall be certified by him to be, from its hilly and broken character, or from some other cause, unavailable for agricultural purposes; such run or portion of a run shall in that case be disposed of by public Auction at the upset price of five shillings per acre, and in accordance with the regulations hereinafter prescribed for auction sales; but such sale shall not take place until after three months' notice of the application to the Commissioner to purchase such land, has been left at some station on the run.