JETS. 1 5 5

angle of divergence is 5° 6', with a length of the converging conenine times the diameter of the smaller base.

If the extremity of the pipe were to have a hollow coneattached to, and around it, and if the combined nozzle and conewere to be surrounded with still water, the outer water wouldbe drawn through the cone, owing to its acquiring part of thevelocity of the jet. By directing a jet of water into a fluid, oraeriform medium, currents are induced which have long beenutilised in various practical ways, such as in the “Jet Pump”(for drawing off flood waters), in “ Giffard’s Injector” (forsupplying water to boilers), and in the “ Steam Injector ” or“ Blast Pipe.”

The application of the hydraulic jet to the propulsion of vesselshas been the subject of experiments of a more or less prac-tical form, and of patents dating as far back as 1661. Düringrecent years the System has been tested by the construction ofseveral vessels which were propelled by hydraulic jets, withthe result of producing mucli controversy amongst experts innaval matters. A paper by Mr. Barnaby (read before theInstitution of Civil Engineers in 1884) gives a description ofthe most recent experiment, in the construction for the Ad-miralty of a torpedo boat by Messrs. Thorneycroft. This wasfixted with a turbine propeller, and the design of this boat pro-vided for utilising as much as possible the velocity of the feedwater. Just in front of the pumps the bottom of the vessel had asudden jump upwards from the stern and towards the bow end.At this point the bottom is formed into a great scoop, whichgeutly rises to the inlet of the pump, which is placed at anangle to reduce the effect produced by the change of directionof the feed-water entering. The velocity of this entering watercauses it to rise in the scoop, and the vanes of the pump areadjusted to pick up the water without shock, and graduallyto accelerate it to the speed of discharge. The peripheralvelocity of the pump is 56 feet per second. The energyacquired by the water is utilised by discharging it throughnozzles to orifices in the vessel above sea-level. These nozzles