The following persons shall be exempt from the provisions of this chapter: (1) An employee or a subordinate of a person holding a license under this chapter, provided the work of such employee shall be under the responsible supervision of a person so licensed; (2) any corporation whose operations are under the jurisdiction of the Department of Public Utility Control and the officers and employees of any such corporation or any contracting corporation affiliated with any such corporation; (3) any manufacturing or scientific research and development corporation and the officers and employees of any such corporation while engaged in the performance of their employment by such corporation, provided the engineering work performed by such corporation, officers and employees shall be incidental to the research and development or manufacturing activities of such corporation; (4) officers and employees of the government of the United States while engaged within this state in the practice of the profession of engineering or land surveying for said government; and (5) architects licensed under chapter 390, in the performance of work incidental to their profession.