Screw pump different applications and handling fluids with varying characteristics. Each ‘screw pump' operates on the same basic principle of a screw turning to isolate a volume of fluid and convey it. However, the mechanical design of each is different. The primary difference is the number of screws: one, two, three or more. The screw pump was described by Archimedes on the occasion of his visit to Egypt. This suggests that the apparatus was unknown to the Greeks before Hellenistic times. A cuneiform inscription of Assyrian king Sennacherib (704–681 BC) has been interpreted by Stephanie Dalley to describe casting water screws in
SS Archimedes lead to the adoption of screw propulsion by the Navy (see Legacy section below). With the conclusion of the Dover trials, "Archimedes" was placed at the disposal of Captain Chappell for a circumnavigation of Britain, which took place in July 1840. This voyage presented an opportunity to not only conduct further tests, but also to allow inspection of the technology by shipowners, engineers and scientists in ports throughout the country. "Archimedes" completed the 2006-mile voyage at an average speed in excess of 7 mph, and a maximum speed under ideal conditions of 10.9 mph. With the completion of this voyage,