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.
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