57.530.  Appointment of deputies and fixing compensation, limits. — The sheriff of the City of St. Louis shall, with the approval of a majority of the circuit judges of the circuit court of said city, appoint as many deputies and assistants as may be necessary to perform the duties of his office, and fix the compensation for their services, which compensation, however, shall not in any case exceed the annual rate of compensation fixed by the board of aldermen of the City of St. Louis therefor.  The annual compensation for sheriff's deputies shall be no less than fifty thousand dollars per year.