The mayor, with the consent and approval of the majority of the members of the board of aldermen, shall have power to appoint a treasurer, city attorney, city assessor, street commissioner and night watchman, and such other officers as he may be authorized by ordinance to appoint, and if deemed for the best interests of the city, the mayor and board of aldermen may, by ordinance, employ special counsel to represent the city, either in a case of a vacancy in the office of city attorney or to assist the city attorney, and pay reasonable compensation therefor, and the person elected marshal may be appointed to and hold the office of street commissioner.