It shall be the duty of every officer so disqualified to report the fact of his disqualification to the Secretary of the Interior or such officer as he may designate as soon as he shall ascertain it, and before the hearing of such cause, who thereupon, with the approval of the Secretary of the Interior, shall designate some other officer or special agent of the Land Department to act in the place of the disqualified officer, and the same authority is conferred on the officer so designated which such officer would otherwise have possessed to act in such case.