Meaning of “deed” in provisions relating to the execution of private documents

(1) In sections 17, 18, 19, 20 and 21, and in all other provisions of this Act relating to proof of the due execution of private documents, “deed” includes for all purposes whatever any letter of attorney or other power, contract or agreement or other instrument “deed” in pro- visions relating (2) Nothing contained in this Act shall apply to the proof of due execution of any instrument with regard to which a special form of execution and mode of proving thereof are prescribed by any law requiring the making of that instrument.