He devoted himself at an early age to the study of oriental languages and became especially proficient in Arabic, under the guidance of Dozy and Juynboll, to whom he was afterwards an intimate friend and colleague. He took his degree of doctor at Leiden in 1860, and then studied for a year in Oxford, where he examined and collated the Bodleian manuscripts of al-Idrisi (part being published in 1866, in collaboration with RP Dozy, as Description de l'Afrique et de l'Espagne). About the same time he wrote Mémoires de l'histoire et de Ia geographie orientales, and edited Expugnatio regionum''. In 1883, on the death of Dozy, he became Arabic professor at Leiden, retiring in 1906.
Though perhaps not a teacher of the first order, he wielded, a great influence during his long professoriate not only over his pupils, but over theologians and eastern administrators who attended his lectures, and his many editions of Arabic texts have been of the highest value to scholars, the most important being his great edition of Tabari. Though entirely averse from politics, he took a keen interest in the municipal affairs of Leiden and made a special study of elementary education. He took the leading part in the International Congress of Orientalists at Algiers in 1905. He was a member of the Institut de France, was awarded the German Order of Merit, and received an honorary doctorate of Cambridge University. At his death he was president of the newly formed International Association of Academies of Science.
Among his chief works are: