In 1906 he became professor at Delft University and this time he got enough resources and students to make his work successful. The same year he became member of the Royal Netherlands Academy of Arts and Sciences. In 1910-1911 he led a geological expedition to Timor. His research at Delft was mainly on the material collected during that expedition, and on the geology of the Netherlands. In 1927 he was a guide of the Shaler Memorial Expedition to South Africa, organized by Harvard University. On the expedition he met Alexander Du Toit, both geologists were among the (at that time rare) supporters of Alfred Wegeners' continental drift theory.
