The Archimedes was a three-masted topsail schooner engined by the Rennie Brothers and launched at Millwall in November 1838. She was driven, not by paddle wheels, but by the new form of screw propellor. She was the first considerable sea-going vessel in the world to be screw propelled. Brunel was asked by the directors of the Great Western Steam Ship company to carry out experiments over a 6 month period on the advantages of the screw propellor. Brunel strongly recommended to the directors the adoption of the screw propellor on the Great Britain as a result of these experiments (see the following lot).