(Subject and without Prejudice to the Liens, Rights, and Remedies herein-before given to the Persons who may become entitled to Compensation for Damage as aforesaid) it shall be lawful for the Duke of Cornwall and his Lessees, and other the Persons authorized by him as aforesaid, and his and their Agents and Workmen, either to pull down, remove, and take away or fill up all Buildings, Steam and other Engines, Machinery, and Things, Pits, Mines, Dams, Sluices, and Works which may be erected or fixed or opened or worked upon any Lands and Tenements in pursuance of the Provisions herein-before contained, and which shall be no longer used for the Purposes aforesaid, or to allow the same to remain for any Time which the Duke of Cornwall or his Lessees, or other the Persons authorized by him, shall think fit, after the same shall have ceased to be used for the Purposes aforesaid; and no Buildings, Mines, Pits, Works, or other Things shall, by Non-user or otherwise, be deemed to be abandoned, so as to vest any Right or Title therein in the Owner of the Land, or to give any fresh Right of Compensation, on the same being resumed or again entered upon and used.