Archivist and historian, born Dublin, Ireland, 1829; died there, 1898. His father was John Gilbert, English Protestant, Portuguese consul at Dublin, his mother Marianne Costello, an Irish Catholic. He was educated at Dublin and Prior Park near Bath. In 1848 he was made a member of the Council of the Celtic Society, in 1855 a member of the Royal Irish Academy and Secretary of the Irish Archaeological Society, and subsequently was affiliated with several important historical and antiquarian societies. For 34 years he was librarian of the Royal Irish Academy. He was a prolific and erudite writer and ranks as one of the greatest historians of his country. Among his works are: "History of the City of Dublin," "History and Treatment of the Public Records of Ireland," and "History of the Viceroys of Ireland."