N.Y. Second Class Cities Law § 12

§ 12. Appointive officers. There shall be appointed by the mayor a\ncorporation counsel, city engineer, commissioner of public works,\ncommissioner of public safety, commissioner of public welfare and sealer\nof weights and measures. The commissioner of public welfare shall be\nappointed in accordance with the provisions of section one hundred\nsixteen of the social welfare law. Other officers may be appointed as\nprovided in this chapter or otherwise by law. All appointments to any\ncity office shall be evidenced by a certificate in writing, signed by\nthe appointing officer and filed forthwith in the office of the city\nclerk. If an appointment be made by the common council such certificate\nshall be signed by the officer presiding at the time the appointment was\nmade and attested by the city clerk.\n