accepted as _prima facie_ evidence. Section 17 regulates the proceedings of the commission. A majority constitute a quorum for the transaction of business. The commission may from time to time make or amend rules for the regulation of proceedings before it. Any party may appear before it and be heard in person or by attorney, and every vote or official act of the commission must be entered of record and its proceedings made public upon the request of either party interested. Section 19 provides that the principal office of the commission shall be in Washington, but that for the convenience of the public it may hold special sessions in any part of the United States. Section 20 authorizes the commission to require annual reports from all common carriers subject to the provisions of the act, to fix the time and prescribe the manner in which such reports shall be made, and to require from such carriers specific answers to all questions upon which the commission may need information. Section 21 excepts from the operation of the act the carriage of property for the United States, State or municipal governments, or for charitable purposes, or for fairs and expositions; also the issuance of mileage, excursion and commutation tickets, the giving of reduced rates to ministers of religion, the free carriage by a railroad company of its own officers and employes, and the exchanging of passes or tickets among the principal officers of railroad companies. The sections not noticed are of minor importance, relating to annual reports, salaries, appropriations of funds, etc. The act was amended on March 2, 1889, but the amendments made did not materially affect its principal provisions.