The annual money value, where ascertained as aforesaid by agreement, may be stated in a memorandum in the form set forth in the said Schedule Gr. hereto annexed, or in a similar form, signed by the parties or their respective agents, and on such memorandum, or the extract decree pronounced by the sheriff, as the case may be, being recorded in the appropriate register of sasines, such annual money value shall be deemed to be feu-duty with all the legal qualities thereof, and shall form an addition to any existing feu-duty, and the superior's right to the carriages and services shall be held to be discharged. Such discharge, redemption, and commutation may be validly effected, notwithstanding the fetters of any entail.