He qualified as a lawyer in 1850, and entered a seminary with the intention of becoming a Catholic priest,[1] but his attention turned to French history and in 1851 he left the École des Chartes with the degree of palaeographic archivist.
He was placed in control of the departmental archives of Aube, and remained in that position until 1880, when he retired on a pension.
He published several volumes of inventorial abstracts, a Répertoire archéologique du département in 1861; a valuable Histoire des ducs et comtes de Champagne depuis le VIe siècle jusqu'à la fin du XIe, which was published between 1859 and 1869 (8 volumes), and in 1880 an instructive monograph, Les Intendants de Champagne.
Already he had become attracted to the study of the ancient inhabitants of Gaul; in 1870 he brought out an Étude sur la déclinaison des noms propres dans la langue franque à l'époque mérovingienne; and in 1877 a learned work on Les Premiers habitants de l'Europe (2nd edition in 2 vols.
He was among the first in France to study the most ancient monuments of Irish literature with a solid philological preparation and without prejudice.