No obliteration, interlineation, or other alteration made in any will after the execution thereof shall be valid or have any effect, except so far as the words or effect of the will before such alteration shall not be apparent, unless such alteration shall be executed in like manner as herein-before is required for the execution of the will; but the will, with such alteration as part thereof, shall be deemed to be duly executed if the signature of the testator and the subscription of the witnesses be made in the margin or on some other part of the will opposite or near to such alteration, or at the foot or end of or opposite to a memorandum referring to such alteration, and written at the end or some other part of the will.