The port commission is hereby authorized, in its discretion, to employ a port director. It shall be the duty of said port director to solicit business for the port, investigate railroad and ocean rates for the protection of the general public in using said port. The salary of the port director shall be fixed by the commissioners with the approval of the mayor and board of aldermen, or the mayor and board of commissioners, and shall be paid from funds derived under the provisions of this chapter, or from the general funds or special funds raised for such purpose in the city treasury; such port commission may, in its discretion, select from its membership a competent person to serve in the capacity of port director, in which case the salary paid such member for services rendered as port director shall not be subject to the restrictions fixed in Section 59-1-5.