Complex sentence: In 1667 he accepted an invitation to succeed Johann Hoornbeck (1617-1666) as professor in, the university of Leiden, but he was drowned with three of his children by the upsetting of a boat while crossing the river Limmat.
Split into simpler sentences: In 1667 he accepted an invitation to succeed Johann Hoornbeck (1617-1666) as professor in the University of Leiden. Before he could take up this position he drowned with three of his children after the upsetting of a boat while crossing the river Limmat.