Correspondence relating to O'Curry's work with the Ordnance Survey and the Royal Irish Academy and general correspondence on antiquarian, genealogical, linguistic and literary matters; correspondence as Professor of Archaeology and Ancient Irish History in the Catholic University, mainly concerning his academic and research interests; some personal correspondence, and personal financial and family documents.

Correspondence relating to Fr Luke Wadding OFM and the Irish Friars Minor at St. Isidore’s College, Rome, on ecclesiastical and political matters; and concerning his interests as historian of the Franciscan Order.

Correspondence between John O'Donovan (1809-1861), and, principally, William Reeves (1815-1892): eighty letters (1832-1860) and twenty-six undated note fragments.