IN MAN'S eternal struggle against the waters the low countries along the North Sea achieved a certain reputation. Today in the Netherlands-a land disdainfully referred to by a Moorish merchant as late as the gth century as a sebcha, or salt water and mud plain'-more than six million people are living in the more than 40 per cent of the total area that lies at or below sea level and in the absence of sea and river dikes is subject to permanent inundation. The island of Rozenburg, in the delta of the Rhine and Maas Rivers (Fig. i), presents an illuminating example of reclamation activities in the Netherlands during the past centuries. Until recently this island, gained entirely from the sea, was serving its inhabitants as an agricultural area, but now it is the scene of the steady expansion westward of the port of Rotterdam, and within a few years it will exhibit the well-known face of an extensive port and industrial area. On the basis of available historical maps and known facts about the history of the island, an attempt has been made here to reconstruct its gradual development. The results are embodied in a series of nine maps.2