The largest part of the collection covers correspondence between Michael Cox and John Dillon and his wife, Elizabeth. The subject matter ranges from Michael’s appointment to the Senate of the Royal University to the health of the Dillon family and invitations to call and visit. Other correspondents include Douglas Hyde and the Archbishop of Dublin, William J. Walsh with whom health and academic issues are discussed. Only a small amount relates to his wife Elizabeth, a cycling register from a family holiday in Donegal; and to his eldest son Aedan, for whom there are only a couple of pieces of correspondence.

The documents relating to Arthur Cox are sparse but wide-ranging in content, from sketch books of sketches that he drew as a boy, to cards celebrating his ordination as a priest at the age of 72. The most comprehensive group of documents is that relating to his time as President of the Incorporated Law Society of Ireland, and includes a scrapbook containing letters, place settings and newspaper cuttings and a photographic album. Also contained is correspondence from relatives who had immigrated to America, to Hugh Cox, Arthur’s grandfather, and Michael.

The collection contains a substantial number of photographs. They range from family snapshots of holidays and outings to formal studio portraits. There are many of Michael Cox and the brothers, Aedan and Arthur, as young boys as well as others of more distant family members.