He then resorted to teaching and to writing for the press, and was an earnest advocate of the Reform Bill of 1832 and of Lord Stanley's Irish education scheme.

[3] On relinquishing this post in 1843, he issued a paper of his own, Duncan's Weekly Register of Politics, Facts, and General Literature.

[1] In 1846, he was appointed by Sir George Gipps sub-collector of customs at Moreton Bay, and soon after settling at Brisbane he was placed on the commission of the peace, made water police magistrate, guardian of minors, and local immigration commissioner.

[1] Duncan, whose acquaintance with modern languages was unusually extensive, translated from the Spanish of Pedro Fernandes de Queiros an Account of a Memorial presented to his Majesty Philip III., king of Spain, concerning the Population and Discovery of the Fourth Part of the World, Australia the unknown, its great Riches and Fertility, printed anno 1610, Spanish and English, octavo, Sydney, 1874, to which he appended an introductory notice.

He was the author of A Plea for the New South Wales Constitution, octavo, Sydney, 1856, of pamphlets on education, and an unpublished history of the colony until the government of Sir George Gipps.