In the absence of census information in Ireland between 1823-1837 the country was surveyed and each occupier listed according to the land held. The Tithes were a tax imposed to support the Established Church (Church of Ireland) which was the official religion at the time of Crown Rule. There is more information on the site and this is indexed by Forename, Surname, Townland, Parish and County. The image is available once a record is selected. The site was indexed by the Latter Day Saints in partnership with the National Archives. http://titheapplotmentbooks.nationalarchives.ie/search/tab/index.jsp Hope this is helpful in identifying the origins of some of your convict ancestors. Gerry in Dublin