Educated guessing. Weaving power. Imagination indispensable. The proving process. Theory gainfully directs both observation and experiment. Tyndall’s views. Discursiveness of Thomas Young 355 XXV. THEORIZING CONTINUED Analogies have value. Many principles may be reversed with profit. The contrary of an old method may be gainful. Judgment gives place to measurement, and then passes to new fields 366 XXVI. NEWTON, FARADAY AND BELL AT WORK Newton, the supreme generalizer. Faraday, the master of experiment. Bell, the inventor of the telephone, transmits speech by a beam of light 387 XXVII. BESSEMER, CREATOR OF CHEAP STEEL. NOBEL, INVENTOR OF NEW EXPLOSIVES Bessemer a man of golden ignorances. His boldness and versatility. The story of his steel process told by himself. Nobel’s heroic courage in failure and adversity. His triumph at last. Turns an accidental hint to great profit. Inventors to-day organized for attacks of new breadth and audacity 401 XXVIII. COMPRESSED AIR An aid to the miner, quarryman and sculptor. An actuator for pumps. Engraves glass and cleans castings. Dust and dirt removed by air exhaustion. Westinghouse air-brakes and signals 417 XXIX. CONCRETE AND ITS REINFORCEMENT Pouring and ramming are easier and cheaper than cutting and carving. Concrete for dwellings ensures comfort and safety from fire. Strengthened with steel it builds warehouses, factories and bridges of new excellence 429 XXX. MOTIVE POWERS PRODUCED WITH NEW ECONOMY Improvements in steam practice. Mechanical draft. Automatic stokers. Better boilers. Superheaters. Economical condensers. Steam turbines on land and sea 446 XXXI. MOTIVE POWERS, CONTINUED. HEATING SERVICES Producer gas. Mond gas. Gas engines. Steam and gas engines compared. Diesel engine best heat motor of all. Gasoline motors. Alcohol engines. Steam and gas motors united. Heat and power production together. District steam heating. Isolated plants. Electric traction. Gas for a service of heat, light and power 457 XXXII. A FEW SOCIAL ASPECTS OF INVENTION Why cities gain at the expense of the country. The factory system. Small shops multiplied. Subdivided labor has passed due bounds and is being modified. Tendencies against centralization and monopoly. Dwellings united for new services. Self-contained houses warmed from a center. The literature of invention and discovery as purveyed in public libraries 478 INDEX 489 LIST OF ILLUSTRATIONS