The idea of propelling vessels by a screw (in lieu of oars) is of ancient date; it is mentioned in the "Machines et Inventions approuvees par l'Acad'emie Rotyale des Sciences depuis 1727 jusqu'a 1731." Franklin long afterwards suggested the same thing, but expressing doubts at the same time of any advantages to be obtained by the plan. In this country a patent was obtained in 1794 by a Mr. Lyttleton for "An Aquatic propeller," consisting of a screw of one, two, or more threads wrapped round a cylinder, and revolving in a frame placed at the head, stern, or side of a vessel. We believe this to be the first patent for a screw propeller.

Various modifications of the screw have since formed the subject of several patents, but it is only within a few years that screw propellers may be said to have come into operation.

Smith's Archimedean Screw Propeller, (1836.) - The annexed engraving represents partly in section the patented invention of Mr. F. P. Smith, to whose perseverance and energy is mainly owing the establishment of screw propelling.

a a is a screw or continuous spiral blade wound round a cylinder b, turning in bearings at c c; at d is a mitred wheel fixed to the shaft, and actuated by the mitred wheel e affixed to the vertical shaft f, at the upper end of which shaft is another mitre wheel g, which is driven by the wheel h fixed upon the engine shaft i; the screw works within an open space formed in the deadwood of the vessel, and the vertical shaft works in a well which is open both at top and bottom, so that the water rises to the level of the water line of the vessel The shaft is steadied by one or more bearings k according to its length.

Mr. Smith constructed a vessel (which he named the Archimedes,) for the purpose of testing the merits of this mode of propelling, and the results were most satisfactory. In July, 1840, the vessel made an experimental voyage round this island, viā Portsmouth, Bristol, Liverpool, Greenock, the Caledonian Canal, Inverness, Leith and Hull, and thence back to London. Up to her arrival at Hull she had steamed 1772 miles in 210 hours, being on an average about 8.2 miles per hour in all weathers and states of the tide. The government subsequently appointed a protracted trial to be made between the Archimedes and the Widgeon, a government steamer propelled by paddle-wheels, and from the success of the experiment were induced to order the Rattler steamer to be constructed with a screw propeller, and in this vessel experiments with various modifications of screws have been made, which have firmly established the efficiency of the screw as a propeller, and it is now employed in numerous government vessels as well as private steamers.

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