The Cathach of St. Columba AD 597 is identified as the copy made by him of a book loaned to him by St. Finnian, and which led to the Battle of Cúl Dreimhne in 561 in Cairbre Drom Cliabh (now in Co. Sligo).
It is the oldest Irish Manuscript dating to 6th Century and came into the possession of the British Institution, Royal Irish Academy in the 1840s, just before the Irish population of Ireland was plunged into famine.
ancients wrote on papyrus, a material that did not grow outside of the Nile Valley. The enterprising Irish perfected a technique of making vellum from hides of calves or sheep, allowing them to replicate church Psalters. In effect, monks became history’s first copying machines. Nevertheless, copying the Bible or a Psalter was a costly endeavor, taking about 400 hides to copy the Old and New Testaments. Irish monk-calligraphers used a writing concept called uncial and later the half-uncial or minuscule – the birth of the lower case alphabet. The primary job of a monk-scribe was to keep track of religious dates, especially the paschal fest, and critical events concerning the monastery. An ancillary benefit involved the recording of societal events, the beginning of western historical writing.
While many of us feel celtic mythology, Finn McCumhail, The Fianna, Oisín and Tír na Nóg were stories handed down through the generations, the majority of these accounts are derived from three ancient Irish manuscript sources. From the late 11th/early 12th century are Lebor na hUidre (it contains the oldest version of the Táin Bó Cuailgne, the Voyage of Bran, the Feast of Bricriú, and other religious, mythical and historical material), the Book of Ballymote, the Book of Lecan. Leabhair na hUidre is currently held in the Royal Irish Academy. which had its beginnings pre 1916 Ireland, specifically in 1785 under Royal charter of King George II. The early 12th century Book of Leinster is in the Library of Trinity College, Dublin, The Book of Glendalough is housed in the Bodleian Library at Oxford University. Despite the dates of these sources, most of the material they contain predates their composition. The earliest of the prose can be dated on linguistic grounds to the 8th century, and some of the verse may be as old as the 6th century.
The majority of Ancient Irish Manuscripts are held in Trinity College, Dublin, The British Library, 96 Euston Road, London, The Bodleian Library, Oxford, The Royal Irish Academy, Dublin.
Important sources include four manuscripts originating in the west of Ireland in the late 14th or early 15th century: The Yellow Book of Lecan, The Great Book of Lecan, The Book of Hy Many, and The Book of Ballymote.