Manner of revoking wills

No will or codicil or any part thereof, shall be revoked otherwise than, 12 (a) by marriage as provided by section 16 of this Act; (b) by another will or codicil executed in accordance with section 7 of this Act; (c) by a written revocation executed in the manner in which the will was executed; or (d) by the burning, tearing or otherwise destroying of it by the testator, or by some person in his presence and by his direction with the intention of revoking it.