Limitation of time for which blocks shall remain set apart.

19. Neither the whole nor any part of any block of land so set aside, shall continue so set aside for a period of more than three years from the date of the Proclamation whereby the same shall be set aside, nor be again set aside under this Act. But every contract made with respect to any such block or any part thereof, whilst the same remains so set aside, shall be performed, notwithstanding that the block has ceased to be so set aside.