I must, however, name a few who gave substantially of their time and effort and without whose help this work would not be as complete as it is. Gilmoure N. Cole, A. L. Rockwell, and the late L. Morgan Porter were major contributors, the latter having made the calculations of the shaking forces, the volumetric efficiency, and the connecting rod characteristics of the 1903 engine. Louis P. Christman, who was responsible for the Smithsonian drawings of this engine and also supervised the reconstruction of the 1905 Wright airplane, supplied much information, including a great deal of the history of the early engines. Opie Chenoweth, one of the early students of the subject, was of much assistance; and I am indebted to R. V. Kerley for the major part of the data on the Wrights' shop engine. Also, I must express my great appreciation to the many organizations that cooperated so fully, and to all the people of these organizations and institutions who gave their assistance so freely. These include the following: Air Force Museum, Wright-Patterson Air Force Base, Ohio Carillon Park Museum, Dayton, Ohio Connecticut Aeronautical Historical Association, Hebron, Connecticut Fredrick C. Crawford Museum, Cleveland, Ohio Historical Department, Daimler Benz A. G., Stuttgart-Untertürkheim, West Germany Engineers Club, Dayton, Ohio Deutsches Museum, Munich, West Germany Educational and Musical Arts, Inc., Dayton, Ohio Henry Ford Museum, Dearborn, Michigan Franklin Institute, Philadelphia, Pennsylvania Howell Cheney Technical School, Manchester, Connecticut Library of Congress, Washington, D.C. Naval Air Systems Command, U.S. Navy, Washington, D.C. Science Museum, London, England Victoria and Albert Museum, London, England In particular, very extensive contributions were made by the Smithsonian Institution and by the United Aircraft Corporation through its Library, through the Pratt & Whitney Aircraft Division's entire Engineering Department and its Marketing and Product Support Departments, and through United Aircraft International. The Beginnings