If any such lands be so released from any such charge or incumbrance, or portion thereof, to which they were subject jointly with other lands, such last-mentioned land shall alone be charged with the whole of such charge, or with the remainder thereof, as the case may be, and the party entitled to the charge shall have all the same rights and remedies over such last-mentioned lands, for the whole or for the remainder of the charge, as the case may be, as he had previously over the whole of the lands subject to such charge; and if upon any such charge or portion of charge being so released the deed or instrument creating or transferring such charge be tendered to the promoters of the undertaking for the purpose, they or two of them shall subscribe, or if they be a corporation shall affix their common seal to a memorandum of such release endorsed on such deed or instrument, declaring what part of the lands originally subject to such charge shall have been purchased by virtue of the special Act, and if the lands be released from part of such charge, what proportion of such charge shall have been released, and how much thereof continues payable, or if the lands so required shall have been released from the whole of such charge, then that the remaining lands are thenceforward to remain exclusively charged therewith; and such memorandum shall be made and executed at the expense of the promoters of the undertaking, and shall be evidence in all courts and elsewhere of the facts therein stated, but not so as to exclude any other evidence of the same facts.