On 2 May 1799, Lanigan accepted a position as assistant librarian and foreign correspondent of the Royal Dublin Society, and began to work on his Ecclesiastical History of Ireland from the first introduction of Christianity among the Irish to the beginning of the thirteenth century, which was not, however, published till 1822 (4 vols., 8vo, Dublin).
2 мая 1799 года Ланиган занял пост помощника библиотекаря и иностранного корреспондента Дублинское королевское общество (англ.), и начал работу над своей Ecclesiastical History of Ireland from the first introduction of Christianity among the Irish to the beginning of the thirteenth century, которая, однако, не была опубликована до 1822 года (4 vols., 8vo, Dublin).