[43] See explanation of system of locating points in Part I, Chap. II, p. 15.
[44] See Balancing of Engines, by Archibald Sharpe.
[45] Except for a ten minute stop to renew the supply of lubricating oil and change the sparking batteries.
[46] See foot-note, page [249].
[47] The weight was afterwards increased to 850 pounds due to repairing the wings and adding more sparking batteries.
[48] See Experiments in Aerodynamics, Smithsonian Contributions to Knowledge, Vol. 27, Washington 1891.
[49] Researches and Experiments in Aerial Navigation, Smithsonian Publication No. 1809, Washington, 1908.
[50] All these minimum permissible conditions are connected by the tacit assumption that the supporting area is not greatly over 2 ft. to the pound of weight. If for instance the weight were increased by larger wings or more wings, furnishing a much greater supporting area per pound, these conditions would not necessarily apply.
[51] These tables were later designated as “Data Sheets.” Several copies, with the data duly entered on them, are given in this appendix, and the form which Mr. Langley included in this letter is therefore not repeated here.—EDITOR.