This information may be notified already but just in case: Find my Past (Free but sign-up) has early census: 1821 - 1851 - fragments as we know: http://search.findmypast.co.uk/search-world-Records/ireland-census-1821-1851?_ga=1.226939166.2014891542.1399081784 But the National Archives (free - no sign-up) has a search facility for the above years and 1901 and 1911 all in one (but they have left my lot out! - sigh) here: http://www.census.nationalarchives.ie/ Good luck in your research. Bryan Chch