The Architect of the Capitol shall have charge of all structural work at the Library of Congress buildings and grounds (as defined in section 167j of this title), including all necessary repairs, the operation, maintenance, and repair of the mechanical plant and elevators, the care and maintenance of the grounds, and the purchasing of all equipment other than office equipment. The employees required for the performance of the foregoing duties shall be appointed by the Architect of the Capitol. All other duties on June 29, 1922, required to be performed by the Superintendent of the Library Building and Grounds shall be performed under the direction of the Librarian of Congress, who shall appoint the employees necessary therefor. The Librarian of Congress shall provide for the purchase and supply of office equipment and furniture for library purposes