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

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.