The Board of Regents shall meet in the city of Washington and elect one of their number as chancellor, who shall be the presiding officer of the Board of Regents, and called the chancellor of the Smithsonian Institution, and a suitable person as Secretary of the institution, who shall also be the secretary of the Board of Regents. The board shall also elect three of their own body as an executive committee, and shall fix the time for the regular meetings of the board; and, on application of any three of the regents to the Secretary of the institution, it shall be his duty to appoint a special meeting of the Board of Regents, of which he shall give notice, by letter, to each of the members; and, at any meeting of the board, eight shall constitute a quorum to do business. Each member of the board shall be paid his necessary traveling and other actual expenses, in attending meetings of the board, which shall be audited by the executive committee, and recorded by the Secretary of the board; but his service as regent shall be gratuitous.