Any surveyor or other person employed by the Commissioners for the purpose of ascertaining the value of any land or buildings which, or the reversion of which, may be vested in the Commissioners under this Act, may enter upon such land or buildings at all reasonable times during the day, upon making full compensation for any damage he may do for the purpose of making a valuation of such land or buildings, or ascertaining the several matters and things necessary to be ascertained by the Commissioners for the purpose of carrying this Act into effect.