As is probably usual with most notes such as this, however short, before completion the author becomes indebted to so many people that it is not practical to record all the acknowledgments that should be made. This I regret extremely, for I am most appreciative of the assistance of the many who responded to my every request. The mere mention of the Wright name automatically opened almost every door and brought forth complete cooperation. I do not believe that in the history of the country there has been another scientist or engineer as admired and revered as they are.

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.