John O’Donovan was born in 1809. His father, though a small farmer, had been descended from the celebrated O’Donovans of County Cork, and when he died in 1817 his son John, then eight years of age and one of a family of nine, was sent to Dublin to be educated. From the age of seventeen he began to devote himself systematically to Celtic study, and three years later was brought under the notice of the Survey Commission as a youth singularly well qualified to conduct the archæological department of their enterprise. Accordingly he entered the service in 1829, and forthwith instituted a careful investigation of the printed books, MSS., and inscriptions bearing on topography; in due course contributing articles to the _Dublin Penny Journal_, and laying the first instalment of his research before the British Association in 1835. Subsequently, Petrie and he published the full report. In 1836 he set about preparing an Analytical Catalogue of the Irish MSS. in Trinity College, and from 1841 was editor of the works published by the Irish Archæological Society. Ever since he undertook the work of the Ordnance Survey, he had in view the idea of writing a _Grammar of the Irish Language_, and after seventeen years’ study the book appeared in 1847, and was received with enthusiasm both at home and abroad. It is characteristic of the way in which British scholarship followed in the rear of that on the Continent, that so well informed and interested an exponent as O’Donovan did not know when he published his valuable Grammar that aspiration and ellipsis had been explained in Germany eight years before then. Thus he arrived too early to benefit much by the study of comparative philology, though deeply interested in the science. His masterpiece is really the edition he issued of the _Annals of the Four Masters_ (1848–51). Of this vast effort Dr. Hyde affirms that it is the greatest that any modern Irish scholar ever accomplished. “So long as Irish history exists, the _Annals of the Four Masters_ will be read in O’Donovan’s translation.” In 1847 he was called to the Bar, but sacrificed his prospects in that line for his Celtic studies. Later, he received the degree of LL.D. from Trinity College, Dublin, and a Government pension of £50 a year, and was appointed Professor of the Irish Language in Queen’s College, Belfast. But having a large family to support on a small income, he contemplated emigrating to America or Australia, when in 1852, most opportunely, the Government resolved to appoint a Royal Commission to publish the ancient Laws and Institutions of Ireland, and he and O’Curry, the two greatest savants on that subject, were chosen for the office. Eight years’ more arduous work undermined his constitution, and he succumbed to an attack of rheumatic fever about the middle of November 1861.