They shall exercise a diligent and faithful supervision of all Public Works in which the State may be interested as Stockholder or Creditor, and shall appoint the Directors in every Railroad and Canal Company, in which the State has the legal power to appoint Directors, which said Directors shall represent the State in all meetings of the Stockholders of the respective Companies for which they are appointed or elected. They shall require the Directors of all said Public Works to guard the public interest, and prevent the establishment of tolls which shall discriminate against the interest of the citizens or products of this State, and from time to time, and as often as there shall be any change in the rates of toll on any of the said Works, to furnish the said Board of Public Works a schedule of such modified rates of toll, and so adjust them as to promote the agricultural interests of the State; they shall report to the General Assembly at each regular session, and recommend such legislation as they may deem necessary and requisite to promote or protect the interests of the State in the said Public Works; they shall perform such other duties as may be hereafter prescribed by Law, and a majority of them shall be competent to act. The Governor, Comptroller and Treasurer shall receive no additional salary for services rendered by them as members of the Board of Public Works.