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August, 1925 to neutralize the bow wave, leaving the surface of the water practically un- disturbed. As the sheet jet moves rear- ward, picking up more water and slowing down, the resultant effect of the jet plus the induced water flow is to deposit water in the place where there is otherwise a depression. Description Of Model Used About three years ago a model was built to test the ideas presented above. This model in its present form is 34.5 feet long; has a mean draft of 1.5 feet, beam 8.5 feet and a dis- placement, as equipped and manned, of 3.1 tons. The model was originally intended to be a ninth scale model of a class 186 destroyer but is not exactly so because of increased draft. The nozzles are two in number, each 9/64 inch wide and 5 inches long and are set so as to direct the jets, when the model is stationary, at 22 degrees on either side of the center line and at about 12 degrees from the hull surface. The model is equipped with a six cylinder gasoline engine and a pump for supplying the jets. Typical Results And Calculations The operation of the model, using jets for propulsion, has resulted in empirical formulas for the behavior of submerged jets. These formulas are new and may require slight cor- rections when more data are avail- able. The other calculations upon which our conclusions are based fol- low from the well-known principles of dynamical similarity for passage from model performance to ship per- formance and the well-known and sim- ple laws of jet reaction. The primary advantage is, of course, more economical propulsion, particu- larly at the higher speeds, and the removal of the speed limiting factor; that is, increasing the practicable speed limit for marine vessels. Screw propeller and shaft troubles are, of course, eliminated. When the jets— that is, the nozzles—come partly out of the water, as a screw does, and for the same reason, there is no variation of load on the prime mover and no tendency to racing; neither is the propulsive effect appreciably re- duced. Reactive thrust is constant. Advantages And Limitations A ship, equipped with induced stream line propulsion, has superior manoeuvering ability. This has been demonstrated with the model used in development. This makes possible broadside movement, as toward or away from a dock, which may be em- ployed in a large ship to cancel set and drift. Stopping and reversing the ship’s motion may be accomplished in much less time and distance than with MARINE REVIEW a screw and in perfect safety to ap- paratus. As bow-wave and wash are mini- mized, the method is suitable for self- propelled canal barges, and the per- missible speed through restricted chan- nels may safely be made very much higher than with a screw or other heretofore available means of propul- sion. The effect of restricted channels on the cost of screw propulsion is well known. Induced stream line prop- ulsion, applied to ships suitable for Great Lakes and coastwise operation, and for operation through the New York State Barge canal has been suggested as the solution of the Barge canal problem and the grain problem of the port of New York. Regardless of low efficiency, ordinary jet propul- sion is now being employed because of inherent advantages, for propulsion on canals abroad. For inland water- ways such as the Mississippi river where the channel is constantly shift- ing, and where logs, snags, sand and mud-bars have to be contended with, induced stream line propulsion is ideal. In a ship propelled by the induced stream line method there is no vibra- tion such as is unavoidably encoun- tered in screw propulsion. The meth- od is likewise advantageous for harbor fire boats wherein the propulsive equip- ment would be available for fire fight- ing. The method cannot be favorably compared to screw propulsion for ap- | plication to tugs or boats designed and used for towing at low speed, where thrust is paramount. The essential apparatus consists of a suitable pump and prime mover, with distribution means, valves and nozzles. Multiple units may be in- stalled, either in series or parallel. All apparatus is obtainable from numerous manufacturers in the open market. Prime movers may be of any type. Centrifugal pumps (single or multi- stage) seem to have much the advan- tage over pumps of other types. They are readily obtainable in sizes suitable to propel any ship: from the very larg- est down to the larger size motor boats, with overall efficiencies rang- ing from 80 to 87.5 per cent. For suitable applications, the cost of equipment and installation will be less than for screw propulsion at the same speed but somewhat more than for screw propulsion per shaft horse- power of the prime mover. Engine room equipment will, gener- ally speaking, occupy no more space than is necessary for the installation of equivalent screw propulsion. The method is particularly adapted to bridge control, since remote control of valves is standard practice. 301 {aon|e. “Ua dhsra} fn TERS YE Marine Ex position in New York—Nov. 9-14 The American Marine exposition in- cluding ports and transportation, will meet in a general marine show in New York at the Two Hundred and Twelfth Anti-Aircraft Regiment arm- ory at Sixty-second street and Colum- bus avenue, Nov. 9 to 14. There will be the most interesting and the widest variety of exhibits ever brought to- gether and every one who buys from or sells to or does both or who is in any way interested in the merchant marine should make it a-point to at- tend this show. Steamship owners are quite likely to think of themselves solely as cus- tomers of the marine industry. How- ever, a large percentage of these other divisions are engaged in world wide trade and make use of ships for ex- port and import cargo and for travel. The. ship owners, who by the way are selling something just as much as any one else, should take an interest in and support by their co-operation all branches of this closely interrelated business so that they may in turn re- ceive whole hearted and loyal sup- port. In the same way the various ports should come out of their shell and display their progress to an in- terested public at this exposition and that is why it has been given the new title used above. A model shipbuilding contest has been initiated and the award will be made at the Marine show, Nov. 10. This contest is for the boy and sea scouts of America. The committee to pick out the winning model will be: Stevenson Taylor, president of the American bureau of shipping, Admiral Leigh C. Palmer, president of the Emergency Fleet Corp., and Admiral J. D. Beuret, chief of the bureau of construction and repair. The models will be displayed at the Marine show and the announcement of the winners will be made there. The boy whe wins first prize will be sent to see the mayor of his city, the governor of his state and the President, and then on a student’s tour of Europe.