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8 MARINE REVIEW. Meager Knowledge Regarding Screw Propellers. One of the editorial writers of tne Engineering Magazine says in the January number: "Considering how long and exten- sively the screw propeller has been employed for marine propul- sion, it might, at first thought, seem remarkable that so little is known of the precise nature of its action under water; but when the difficnlty (not to say impossibility) of actual observation is taken into account, it is not so much to be wondered at. No theory of propeller action has yet been framed tha' can be relied upon as taking fully into account all the conditions dependent upon various forms of hulls, rates of speed, and position with reference to the hulls of vessels; and it is a well-known fact that, to get the best results from engines of a given power, it is fre- quently necessary to try one propeller after another until the one best fitted for use with a particular ship is found by actual ex- periment--examples of cases where mere theorizing utterly fails to guide selection. So we are still in the dark upon the subject, and though, doubtless, gaining a little light as time progresses, it is likely to be some time yet before a screw propeller can be selected in advance for a particular ship, with the certainty that it will prove the best possible when the trial trip is made. "Of screw-propellers something has been printed editorially in the Engineer (London) recently. The topic is the limits of improvement yet possible in screw-propellers. It is obvious that no form of propeller-blade or modification of the boss to which these blades are attached--no reduction or increase of the num- ber or particular arrangement of the blades--can enable a screw- propeller to develop, even theoretically, a mechanical power in thrust any greater than that developed by the engines that drive it. Practically every one admits that the power of the thrust in foot-pounds must be less than the power developed by the mo- tors, by the total power expended in overcoming passive resist- ances. How much less is it in present practice? The editorial referred to makes the point that the limit of improvement must lie within the present margin of loss of power as developed in thrust, and the unavoidable loss in engine friction that experience and skill has not been able to reduce below from 10 to 12 per cent. We may, therefore, place the theoretical limit of the power possible to be represented by the thrust of the propeller, or, more appropriately speaking, the net work applied by the screw to actual propulsion, as about 88 per cent. of the power developed by the engines driving it. Now, upon this point the Engineer asserts: 'It may be taken as proved that about 80 per cent. of the quality of a screw is fixed by blade area, so that, given blade area enough and regarding 100 as representing perfection, the worst screw it is possible to make will not be 20 per cent. worse than the best.' Here then, if the proposition made be accepted as true, we have the limits between present practice and theoret- ical possibility cut down to 20 per cent. of the total theoretical possibility. It is to be doubted whether all marine engineers, or perhaps a majority of them, will accept the proposition without challenge. It is certain that in practice there are anamolous pe- culiarities in the action of propellers. For instance, on one of the English warships a great variety of propellers were tried before the propulsive power developed could be made satisfactorily com- mensurate with the power of her engines; and when this result, after tedious experiment and much expense, was at last secured, no one could say with certainty why the successful screw was more efficient than others that were tried and found wanting. The Engineer, in the course of its long argument, quotes from text-books that 'the efficiency of the propeller is 50 or 60 per cent.' and upon this remarks that 'unless very serious mistakes are to be risked, it is necessary that in all cases the sense in ial the word efficiency is employed shall be very sharply de- ned' "Mr. Isherwood's definition (thrust multiplied into speed of the ship and compared with the indicated horse-power) it thinks misleading to the last degree; however, it admits that 'no one seems able to devise a better measure of efficiency,' all of which is confirmatory of the meager knowledge of the exact nature of the action of a screw in a fluid medium.' Admiralty Docket at Detroit. Judge Swan of the United States district court, Detroit, has made the following assignment for hearing of admiralty cases: Friday, January 6, 1893--4058, Stephen B. Grummond ys. steam barge Isabella J. Boyce; 4156, Albert Forest vs. Benjamin Boutell and Peter C. Smith. ; Tuesday, January 10--3771, Henry and Frederick White vs. steam barge Laketon; 3849, Chickory Connelley and another vs. schooner Aloha; 3858, Daniel L. Runnels and another vs. schooner James KE. Gilmore; 3908, Stephen B. Grummond vs. schooner Mineral State. Wednesday, January 11--3909, Stephen B. Grummond vs. schooner E. R. Williams; 3914, Ella Bowers vs. schooner Lone Star; 3936, Capel R. Emery vs. tug Gracie A. Ruelle. Thursday, January 12--3944, Ellen Craig vs. schooner ieee Card; 3973, James Henry Goodwin vs. tugs Runnels and Kittie Haight ; 3975, John Mullerweiss, Jr., vs. pile driver He Ora. Friday, January 13--3743, Henry N., Land vs. steamer Frontenac; 4009, Annie Sullivan vs. Edward Gilmore, et al; 4019, William Baxter vs. barge Sweepstakes. Saturdry, January 14--4024, John F. Eddy et al vs. schoon- er Pelican; 4039, Benjamin Boutelle et al vs. Carl Heavenrich : 4045, the Boy Line & Fire Boat Company vs. barge Ida Corning ; 4090, Gus Gravell vs. barge Bottsford. Monday, Jan. 16--4044, the Gratwick, Smith & Fryer Lum- ber Company et al vs. schooner D. P. Dobbins; 4046, Emil Girard vs. schooner Republic. Tuesday, January 17--4047, Loveland Transportation Com- pany vs. propeller John M. Nicoll; 4055, Decatur B. Millen et al vs. Eureka Fire and Marine Insurance Company; 4064, Osias W. Shipman vs. tug Gordon Beebe; 4097, Frank J, Willette, administrator. vs. propeller John M. Nicoll. Wednesday, January 18--4068, John E. Pickette vs. schoon- er Senator Blood; 4070, United States vs. 1,150% pounds cellu- loid ; 4087, Gillette Surles vs. steam barge Maud Preston. Thursday, January 19--4092, Peter Kerwin vs. scow Louise; 4094, Farwell 'Transportation Company et al vs. Union Marine Insurance Company; 4125, James Carroll vs. propeller F. & P. M. No. 2. €. ; Friday, January 20--4145, Hollister Transportation Com- pany vs. 500,000 feet pine lumber; 4148, United States vs. two trunks and two valises containing opium. Saturday, January 21--4149, Charles H. Weeks vs. propel- ler Toledo; 4155, Union Dry Dock Company et al vs. tug Sea Gull. Tuesday, January 24--4023, the Interlake Transportation Company vs. steamer Brazil. Wednesday, January 25--4085, Andrew St. Martin et al vs. propeller Henry F. Packer; 4098, John Stevenson vs. 333% and 323 cords cedar; 4103, Andrew J. Wilson vs. steamer A. J. Wright. Thursday, January 26--4118, Carlos Libert vs. Kureka Fire & Marine Insurance Company; 4121, Delos E. Rice et al vs. steam yacht Countess ; 4122, Charles Towse et al vs. barge S. A. Irish. Friday, January 27--4135, Sarah HE. Duntord et al vs. schooner Mary; 4136, Thompson W. Thompson, administrator, vs. Detroit & Cleveland Steam Navigation Company ; 4140, Timothy Hurley et al vs. steamer City of Mackinaw; 4146, Mary A. Hurley, administratrix, vs. Detroit & Cleveland Steam Navigation Company. Saturday, January 28--4062, Thomas Dunford et al vs. schooner Hunter Savidge ; 4163, Charles EK. Kastman et al vs. propeller Pasadena. Tuesday, January 31--4179, Timothy L. Churchell et.al vs. steamer F. W. Wheeler and Barge Ashland; 4134, F. W. Gil- christ et al vs. steamers Fontana and Caliyuga ; 3967, Cooley vs. barge Magnet. Wheat and Corn in Store at Lake Ports. The following table, prepared from reports of the Chicago board of trade, shows the stocks of wheat and corn in store at the principle points of accumulation on the lakes on Dec. 31, 1892: Wheat, bu. Corn, bu. GIMICAG OW ais sesttae eet vavk sada: II, 750,000 5,048,000 Duluth. .......00..0.0eeee eseeeeee WA WAVE OO OW tr = stnaeoieas Milwaukee Geen colnet eae 2,278,000 31,000 Detrotterrcgsaiye-. <ledcavaveticns 1,746,000 34,000 PINON Osc ints sociated ne avirtowns 3,594,000 669,000 Bila al@ienee asset segers ce as sstene 4,261,000 160,000 Mota li cise snares coe 38,064,000 5)942,000