The idea of using the reaction of a jet of water pumped sternwards from a ship is endowed with a respectable antiquity, but tests on the efficiency of such propellers, whether model or full-scale, have not been extensive. Perhaps the most thorough tests were those of S. W. Barnaby (Thornycroft and Co.) in 1880, described by him in the Proceedings of the Institute of Civil Engineers, Vol. LXXVII, page 1, 1883. This investigator measured the reaction on a nozzle delivering water under pressure into still water by a force balance connected to the nozzle itself. As a result, the “ Waterwitch,” a vessel of 1,160 tons, was constructed to work on this principle, the jet being supplied by a centrifugal pump which took water from a scoop amidships. The efficiency of the jet itself worked out at .71, but with the pump the combined efficiency was only .38.