Post mill, model, late 17th/early 18th century. In the first half of the 17th century many areas of the Dutch Republic were drained. This reclaimed land - polder - was intended for agriculture. Windmills were used to pump out the water from the lakes. And it was the windmill that provided the power needed to keep the land dry. Post mills were designed so that the top half could turn in every direction to catch the wind. In this mill a screw contained in a cylinder raised water as it turned. This invention dates from around 1640 and enabled engineers to drain even the deepest Dutch lakes.