In 1847, John Mitchel launched the "United Irishman", the newspaper of the militant Young Ireland Movement. He was charged with treason and sentenced to 14 years and transportation to Van Diemen's land (Tasmania). After his escape to New York, where he edited the "Citizen", he made many Roman Catholic enemies because of his criticism of the temporal power of the pope. His "Jail Journal" was published in 1854.
Young Ireland in Exile by J.H. Cullen
Irish Exiles in Australia by T.J. Kiernan