De Westermolen, Kollumerpomp of the upright shaft. At the bottom of the upright shaft is the "crown wheel", which has 41 cogs, drives a gearwheel with 42 cogs on the axle of the Archimedes' screw. The axle of the Archimedes' screw is diameter. The screw is diameter . It is inclined at 16.7°. Each revolution of the screw lifts of water. The Archimedes' screw that pumped water into the polder has been removed. "De Westermolen" is open on Friday mornings. It is also open on Saturday mornings if there is enough wind to work the mill. De Westermolen, Kollumerpomp De Westermolen is a
SS Archimedes fitted with Smith's patented propeller, "Princess Royal", was built in the north of England, and in 1842, several more screw-propelled vessels were built or launched in Britain, including "Bedlington", built at South Shields, "Bee", launched at Chatham, and the largest ship built to that date in Ireland, "Great Northern", launched at Derry. From this point, screw-propelled merchant ships grew rapidly in number. By the time the Cunard Line built the paddle steamer "Persia" for transatlantic service in 1856, the paddlewheel was already becoming an anachronism. Though Smith's "Archimedes" had played an important role in the introduction of screw propulsion, Smith