The mayors of cities of the second and third class shall supervise the conduct of all city officers, examine the grounds of all reasonable complaints made against any of them, and cause all of their violations or neglect of duty to be promptly punished, or reported to the proper tribunal for correction; and for the purposes aforesaid he is hereby empowered to issue subpœnas and compulsory process for the production of such persons and such books and papers as he may deem necessary.