By all accounts Michael O’Brien, that fine scholar and most generous and unassuming of men, was not happy about his Corpus genealogiarum Hiberniae, vol. i. He had it in hand for years and spent an incalculable mount of meticulous labour on it, but only near the end of his life, with great reluctance, did he consent to its publication. The proofs lacked what he considered final correction, and he feared leaving a legacy of avoidable error. Of course what he did leave was an instrument of scholarship, the value and uses of which other men will be decades in proving out. To our gratitude for his learning and labours we should therefore add an almost equal gratitude to those friends who insisted that he publish despite the probability that residual error might still amount to a fraction of one per cent. Our thanks may indeed be the greater since we learn from the introduction that this volume was intended as the first ‘of a series to contain all important Irish pedigrees and genealogical material from the earliest literary period down to c. 1500 A.D.’. If it seems unlikely now that we shall see vol. ii or any of the others, we might so easily not have had even vol. i.