 In 1839 he assisted Charles Gavan Duffy and other Catholics in Belfast to establish "The Vindicator" newspaper to which he contributed, the paper supported the Daniel O'Connell and catholic emancipation.Dr Crolly published a number of volumes on Moral Theology and a biography of his uncle Archbishop William Crolly.Crolly died on the 24th of January, 1878 and is buried in Maynooth College graveyard.