Essentially, it is a large screw, open at both ends and encased lengthwise in a watertight covering. When one end of the screw is placed in water and the screw is elevated at an angle and then turned, ...

Essentially, it is a large screw, open at both ends and encased lengthwise in a watertight covering. When one end of the screw is placed in water and the screw is elevated at an angle and then turned, ...