Archimedes was a mathematician and inventor from ancient Greece. He discovered the relation between the surface and volume of a sphere and its circumscribing cyclinder (he had discovered pi). He then formulated a hydrostatic principle based on that mathmatical relationship called Archimedes' principle. He inventing the Archimedes screw - a screw-shaped machine or hydraulic screw that raised water from a lower to a higher level. Archimedes also invented the catupult, the lever, the compound pulley, and the burning mirror (a system of mirrors that burned the boots and ships of invading armies by focusing the sun's rays). Although Archimedes is credited with inventing the screw in the 3rd century BC, his screw was not like today's screw fastener but actually two other screw-type devices.