ARCHIMEDES

archimedes, screw of, a machine for raising water, said to have been invented by archimedes, for the purpose of removing water from the hold of a large ship that had been built by king hiero ii. of syracuse. it consists of a water-tight cylinder, enclosing a chamber walled off by spiral divisions running from end to end, inclined to the horizon, with its lower open end placed in the water to be raised. the water, while occupying the lowest portion in each successive division of the spiral chamber, is lifted mechanically by the turning of the machine. other forms have the spiral revolving free in a fixed cylinder, or consist simply of a tube wound spirally about a cylindrical axis. the same principle is sometimes used in machines for handling wheat, &c. (see conveyors).