Wilbur and Orville acknowledged Otto Lilienthal, a famous German pioneer in aviation, as their greatest inspiration. Recognized as the father of gliding, Lilienthal made hundreds of glides with various apparatuses employing birdlike wings. First to explain scientifically why curved surfaces in a flying machine are superior to flat surfaces, Lilienthal’s work on wing surfaces and air pressure proved valuable to the Wrights. Interested in scientific affairs, the brothers read with fascination and excitement, reports in 1895 of gliding flights by Lilienthal. But the art of gliding was neither a game nor child’s play for aviation’s pioneers. Lilienthal crashed and died as a result of a glider accident in 1896. Reading of his death, the Wrights wondered if they could go on from where he had left off. [Illustration: _Courtesy, Smithsonian Institution._] [Illustration: Octave Chanute (1832-1910).] [Illustration: Samuel Pierpont Langley (1834-1906).] Eventually the Wrights were ready to begin “a systematic study of the subject in preparation for practical work,” and hoped to make contributions “to help on the future worker who will attain final success.” Searching for, but finding little material on attempts to fly in the Dayton Public Library, Wilbur wrote, in May 1899, to the Smithsonian Institution in Washington seeking information about publications to read on aeronautics. The list of books and articles suggested by the Smithsonian included works by Dr. Samuel P. Langley who later became its director and secretary. The brothers were encouraged by seeing that a man of Langley’s scientific standing believed in the possibility of flight at a time when few people did. Langley had been making aeronautical studies and experiments and succeeded in building power-driven models that flew. Later he built and attempted to fly a full-size, man-carrying powered machine; but in this he failed. When a model flies, it does not necessarily follow that a full-size machine of the same design will also fly. As boys Wilbur and Orville had built model Pénaud helicopters that flew, but even the Wrights could not later have built a successful man-carrying machine by merely following Pénaud’s same general design. The difficulty is—as early experimenters with model machines unhappily discovered—that when the linear measurement of a model is doubled it needs about eight times the power to make it fly. Among the sources suggested by the Smithsonian was Octave Chanute’s _Progress in Flying Machines_. Chanute, a successful construction engineer living in Chicago, had directed experiments with gliders of his own design. A longtime encouraging friend and adviser to the Wrights, Chanute made an exhaustive study of the history of aeronautics. _Problems of Flight_