MARINE ENGINES.

379

and whose full propelling area is only attained when the arms towhich they are bolted are vertical Thus when fixed the floatsdepress the water on entering, and tend to lift it when leaving, and

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to obviate this difficulty each float was formerly stepped, or madein two or more separate pieces, placed one before another. Thisplan, however, is now become almost obsolete; the feathering floats,although somewhat complicated, being generally adopted for all