His father, James Dunn, the master of a small trading vessel, made the acquaintance of John Wesley in 1768, and became a class leader; with his crew he protected Adam Clarke from the fury of a mob in Guernsey in 1786.
Dunn was afterwards stationed at Newcastle, Rochdale, Manchester, Sheffield, Tadcaster, Edinburgh, Camborne, Dudley, Halifax, and Nottingham successively, and at all these places proved a most acceptable preacher.
His best-known works are A Dictionary of the Gospels, with maps, tables, and lessons, published in 1846, which went to a fourth edition in the same year, and Memoirs of seventy-five eminent Divines whose Discourses form the Morning Exercises at Cripplegate, St. Giles-in-the-Fields, and Southwark, which appeared in 1844.
In 1849, Dunn started publishing a monthly magazine called the Wesley Banner and Revival Record, which, following the example set by the Fly Sheets, criticised the governance of Methodism and suggested reforms.
In a short time 20,000 copies were sold of a small pamphlet entitled Remarks on the Expulsion of the Messrs. Everett, Dunn, and Griffith by William Horton.
degree by one of the United States universities, and after that event called himself minister of the Methodist Episcopal Church of America.