'The employment of jet propulsion in submarines, in lieu of screw propellors', memorandum by H R Norbury Referring to tests on a hydraulic system of torpedo boat propulsion tested by Thornycroft in 1883. The prototype method was no better than the use of propellers, but subsequent improvements in circulating pumps might influence the question: 'what is the practicabilityof applying hydraulic propulsion to a submarine of say 1,000 tons?' Marked 'Secret'. [29 November 1915]