This volume celebrates the work of William O’Sullivan, the first keeper of manuscripts at Trinity College, Dublin, who preserved, made more accessible and elucidated the documents in his care. The manuscripts throw new light on the society of Ireland, the place of the learned and literate in that world, and its relations with Britain, Europe and America. Some of these essays clarify technical problems in the making of famous manuscripts, and bring out for the first time their indebtedness to or influence over other manuscripts. Others provide unexpected new information about the reigns of Edward I and James I, Irish provincial society, the process and progress of religious change and the links between settlements in Ireland and North American colonization.