N.H. Rev. Stat. Ann. § 112:2

In case the head of any state department or institution, or a member of any state agency, board or commission, except a per diem or uncompensated member, has entered or is ordered into or enlists in the armed forces of the United States in connection with the strengthening of the national defense in an emergency, the governor, with the approval of the council, may appoint an acting head or member who shall have all the powers, perform all the duties and assume all the responsibilities of the person for whom he is acting, except that the supreme court may appoint any such acting members of the board of tax and land appeals.