At the National Physical Laboratory , Teddington . The new marine testing tank , 678 ft long , 20 ft wide and depth of water of 9 ft . Model towing carriage , which can tow model ship hulls up to speeds exceeding 30 ft per second . It is electrically driven with current supplied by overhead wires seen in photograph . Apparatus for testing propellers . The propeller is held on a shaft in front of the body and complete records taken of its behaviour , so that by testing several the best screw for any particular ship can be found . 14 November 1932