No contract for the supply of coal to the Board for the Board’s use shall be made except by public tender of which public notice shall have been given on at least two occasions in a newspaper circulating in the district, and no member of the Board who is carrying on the business of coal-mining or who is a member of a firm, company, society, or association (whether incorporated or not) carrying on the business of coal-mining shall take part in the discussion on, or vote upon the question of, the acceptance of any such tender, and the Board in letting any such contract shall be governed by the decision of the majority of the remaining members of the Board who are present at a special meeting of such members called in accordance with the provisions of section twenty-six of the Local Railways Act, 1914, for the purpose of considering tenders for such supply; and in the event of an equality of votes such members shall appoint an umpire whose decision shall be final.”