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THE GROWTH OF THE STEAM-ENGINE.
541
Messrs. Stevens. The hull of the Phoenix had hollow water-lines sixty-five years ago, and this important characteristic of modern vessels is, therefore, an American improvement.
Fig. 63.—The Two Rhode-Islands, 1836-1876.
The North America (Fig. 64) was built in 1827. The hull was stiffened by the "hog-frame," now as distinctive a characteristic of the vessel as are the gallows-frame and the skeleton-beam of the engine.
This engine is not usually quite as economical in fuel as are the screw-engines last described; but it has the advantages—which are so extremely important in the shallow, flexible hulls of our river-boats
