He was a historian and the first director of the Commissie van Advies voor ‘s Rijks Geschiedkundige Publicatiën, which later on became the Institute of Dutch History. Since 1908 he was a member of the Royal Netherlands Academy of Arts and Sciences. Between 1918 and 1925 he worked as a History professor at Leiden. He published several books on the subject of Dutch emigration. In 1933 he was accused of plagiarism by two of his colleagues but the accusation was unfounded.