The Semi-Portable Engine, 348; Performance of Portable Engines, 350; their Efficiency, 352; the Hoadley Engine, 354; the Mills Farm and Road Engine, 356; Fisher's Steam-Carriage, 356; Performance of Road-Engines, 357; Trial of Road-Locomotives by the Author, 358; Conclusions, 358; the Steam Fire-Engine, 360; the Rotary Steam-Engine and Pump, 365; the Modern Locomotive, 368; Dimensions and Performance, 373; Compound Engines for Locomotives, 376; Extent of Modern Railroads, 378; SECTION III.--MARINE ENGINES. 379 The Modern Marine Engine, 379; the American Beam Engine, 379; the Oscillating Engine and Feathering Wheel, 381; the two "Rhode Islands," 382; River-Boat Engines on the Mississippi, 384; Steam Launches and Yachts, 386; Marine Screw-Engines, 389; the Marine Compound Engine, 390; its Introduction by John Elder and others, 393; Comparison with the Single-Cylinder Engine, 395; its Advantages, 396; the Surface Condenser, 397; Weight of Machinery, 398; Marine Engine Performance, 398; Relative Economy of Simple and Compound Engines, 399; the Screw-Propeller, 399; Chain-Propulsion, or Wire-Rope Towage, 402; Marine Steam-Boilers, 403; the Modern Steamship, 405; Examples of Merchant Steamers, 406; Naval Steamers--Classification, 409; Examples of Iron-Clad Steamers, 412; Power of the Marine Engine, 415; Conclusion, 417. CHAPTER VII. THE PHILOSOPHY OF THE STEAM-ENGINE. THE HISTORY OF ITS GROWTH; ENERGETICS AND THERMO-DYNAMICS 419