Historical overview of hydraulic engineering in the Netherlands until 1960. The author wrote the main part of this book during the second world war. The author (1893-1959) advocated at that time strong improvement of the Dutch sea defences, but this was politically not accepted. For that he used the pseudonym "Dr. Cassandra". After 1953 he became the "father" of the Deltaworks, described in the last chapter of this book (which was updated by Stuvel).