Railway and Turnpike Roads compared. -- Mr. Gurney's inventions. -- His Locomotive Steam Engine. -- Its performances. -- Prejudices and errors. -- Committee of the House of Commons. -- Convenience and safety of Steam Carriages. -- Hancock's Steam Carriage. -- Mr. N. Ogle. -- Trevithick's invention. -- Proceedings against Steam Carriages. -- Turnpike Bills. -- Steam Carriage between Gloucester and Cheltenham. -- Its discontinuance. -- Report of the Committee of the Commons. -- Present State and Prospects of Steam Carriages. 213 CHAPTER XII. STEAM NAVIGATION. Propulsion by paddle-wheels. -- Manner of driving them. -- Marine Engine. -- Its form and arrangement. -- Proportion of its cylinder. -- Injury to boilers by deposites and incrustation. -- Not effectually removed by blowing out. -- Mr. Samuel Hall's condenser. -- Its advantages. -- Originally suggested by Watt. -- Hall's _steam saver_. -- Howard's vapour engine. -- Morgan's paddle-wheels. -- Limits of steam navigation. -- Proportion of tonnage to power. -- Average speed. -- Consumption of fuel. -- Iron Steamers. -- American steam raft. -- Steam navigation to India. -- By Egypt and the Red Sea to Bombay. -- By same route to Calcutta. -- By Syria and the Euphrates to Bombay. -- Steam communication with the United States from the west coast of Ireland to St. Johns, Halifax, and New York. 241 CHAPTER XIII. GENERAL ECONOMY OF STEAM POWER. Mechanical efficacy of steam -- proportional to the quantity of water evaporated, and to the fuel consumed. -- Independent of the pressure. -- Its mechanical efficacy by condensation alone. -- By condensation and expansion combined -- by direct pressure and expansion -- by direct pressure and condensation -- by direct pressure, condensation, and expansion. -- The power of engines. -- The duty of engines. -- Meaning of horse power. -- To compute the power of an engine. -- Of the power of boilers. -- The structure of the grate-bars. -- Quantity of water and steam room. -- Fire surface and flue surface. -- Dimensions of steam pipes. -- Velocity of piston. -- Economy of fuel. -- Cornish duty reports. 277 CHAPTER XIV. Plain Rules for Railway Speculators. 307 THE STEAM ENGINE EXPLAINED AND ILLUSTRATED. CHAPTER I. PRELIMINARY MATTER.