. A sketch of the origin and progress of steam navigation from authentic documents. he entrance of thecommon board. These split paddle-boardsare as efficient in propellingwhen at the lowest point asthe common paddle-boards,and when they emerge thewater escapes simultaneouslyfrom each narrow board, andis not thrown up, as is thecase with common paddle-boards.* A large number of vesselsare fitted with this form ofwheel; the Great Westernis among the number. The unfortunate steamship the President had a pair of such wheels during some of hervoyages; but her proprietors, rather than pay the requir
. A sketch of the origin and progress of steam navigation from authentic documents. he entrance of thecommon board. These split paddle-boardsare as efficient in propellingwhen at the lowest point asthe common paddle-boards,and when they emerge thewater escapes simultaneouslyfrom each narrow board, andis not thrown up, as is thecase with common paddle-boards.* A large number of vesselsare fitted with this form ofwheel; the Great Westernis among the number. The unfortunate steamship the President had a pair of such wheels during some of hervoyages; but her proprietors, rather than pay the required patentright, had them removed, and replaced by the common wheels. This circumstance is not mentioned invidiously, but as a matter ofhistory. It is not supposed that the change of wheels had the slightestconnection with the loss of the ship. * A patent was subsequently obtained for these by Mr. Elijah Galloway on the 18thAugust, 1835. - Mr. Field did not persevere in its use at the time he invented it.— on Steam Engine, Steam Navigation, and Railways. London, STEAM NAVIGATION. 109 The specification and other particulars in connection with this pa-tent may be found in several scientific journals * Many modificationsof the paddle-wheel have been patented, and experimentally tested;but it may be said that the three last described inventions only arenow generally in use. Various patents have also been granted, at different periods, foranother instrument for propelling vessels, commonly denominated The Screw Propeller. One form of the instrument is that of a blade, or blades, cut froma plane, and placed at an angle on an axis, similar to the blades ofa smoke-jack, as ordinarily made. A second form is that in which the blades resemble those of atruly formed screw of one or two turns in length, or sections of ascrew of less than one turn in length; the latter being similar to thosepatented by Captain Ericsson in 1836, and shown in the drawing ofthe machinery fitte
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