SECTION 18. That each Commissioner shall receive an annual salary of seven thousand five hundred dollars, payable in the same manner as the judges of the courts of the United States. The Commission shall appoint a secretary, who shall receive an annual salary of three thousand five hundred dollars, payable in like manner. The Commission shall have authority to employ and fix the compensation of such other employees as it may find necessary to proper performance of its duties. Until otherwise provided by law, the Commission may hire suitable offices for its use and shall have authority to procure all necessary office supplies. Witnesses summoned before the Commission shall be paid the same fees and mileage that are paid witnesses in the courts of the United States.

All of the expenses of the Commission, including all necessary expenses for transportation iucurred by the Commissioners, or by their employees under their orders, in making any investigations or upon official business in any other places than in the city of Washington, shall be allowed and paid on the presentation of itemized vouchers therefor approved by the chairman of the Commission.