The fourth award of the Vetlesen Prize for outstanding accomplishments in sciences of the Earth and the Universe was made October 18, 1966, at Columbia University to Jan Hendrik Oort, Director of the Observatory and Professor of Astronomy of the University of Leiden, The Netherlands.This Prize, which was established in Columbia University by the G. Unger Vetlesen Foundation in 1959, is an outstanding award, comparable to the Nobel Prizes in other sciences, carrying not only the distinction and the honor but a cash prize of $25,000 and a gold medal.