Langley's Memoirs of Mechanical Flight, Parts I and II. Smithsonian Contributions to Knowledge, Volume 27, Number 3, Publication 1948, 1911, was written by two authors: Samuel Pierpont Langley and Charles Matthews Manley. These memoirs highlight the revolutionary advances in aviation and mechanical flight research that took place in the first half of the 20th century. The authors describe in detail the stages of the discovery and study of the laws of aerodynamics, the construction of aircraft and the attempt to make the first successful manned flight. Their documented scientific observations and conclusions became an important contribution to the development of the aviation industry and technology. Langley's Memoirs of Mechanical Flight is a must-read for anyone interested in aviation history and research.