This collection consists of seven volumes written by John M. Cotter and reflecting his interests in linguistics, astronomy, botany, and the history of the Celtic people. Several of the volumes are commonplace books that include copies of letters, personal accounting, vocabulary and drafts of translations, recipes, notes on astronomy, and information on plant propagation and care. Other volumes are devoted to his translations, including a fair copy of his manuscript translation of King Cormac's Glossary (Sanas Cormaic), an Irish grammar, an Irish version of "The Catholic Children's Religious Primer," and "The Folklore of Waterford," also in Irish. The collection also contains Cotter's translation of and theories about the Mayan book the Chilam Balam of Chumayel. There is a small amount of loose material in the books, consisting of translations, notes, ephemera, correspondence, a deed, and loan documents.