Note: Project Gutenberg also has an HTML version of this file which includes the numerous original illustrations. See 47981-h.htm or 47981-h.zip: (http://www.gutenberg.org/files/47981/47981-h/47981-h.htm) or (http://www.gutenberg.org/files/47981/47981-h.zip) Images of the original pages are available through Internet Archive/American Libraries. See https://archive.org/details/langleymemoironm00lang Transcriber's note: The original page numbers (example: [p052]) are included in the text to facilitate use of the index. Text enclosed by greater-than or less-than symbols is in italics (<italics>). Small capitals have been trascribed as ALL CAPITALS. Underscores are used to denote subscription. A single character following an underscore is subscripted (example: H_2O). Multiple subscripted characters are enclosed by curly brackets (example: ‹P›_{90}). A carat character is used to denote superscription. A single character following the carat is superscripted (example: ‹n›^2). Multiple superscripted characters are enclosed by curly brackets (example: sin^{−1}). Some characters might not display in this UTF-8 text version or in the html version. If so, the reader should consult the original page images referred to above. An additional transcriber's note is at the end of the text. Smithsonian Contributions to Knowledge Volume 27 Number 3 LANGLEY MEMOIR ON MECHANICAL FLIGHT PART I. 1887 TO 1896 by SAMUEL PIERPONT LANGLEY Edited by Charles M. Manly PART II. 1897 TO 1903 by CHARLES M. MANLY Assistant in Charge of Experiments [Illustration] (Publication 1948) City of Washington Published by the Smithsonian Institution 1911 Commission to whom this Memoir has been referred: Otto Hilgard Tittman, George Owen Squier, Albert Francis Zahm. The Lord Baltimore Press Baltimore, MD., U. S. A. 67009 [page iii] ADVERTISEMENT The present work, entitled “Langley Memoir on Mechanical Flight,” as planned by the late Secretary Samuel Pierpont Langley, follows his publications on “Experiments in Aerodynamics” and “The Internal Work of the Wind” printed in 1891 and 1893, respectively, as parts of Volume 27 of the Smithsonian Contributions to Knowledge. This Memoir was in preparation at the time of Mr. Langley’s death in 1906, and Part I, recording experiments from 1887 to 1896, was written by him. Part II, on experiments from 1897 to 1903, has been written by Mr. Charles M. Manly, who became Mr. Langley’s Chief Assistant in June, 1898. The sources of information for this Part were the original carefully recorded accounts of the experiments described. It is expected later to publish a third part of the present memoir, to consist largely of the extensive technical data of tests of the working of various types of curved surfaces, propellers, and other apparatus.