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Wilbur Wright, [Observations on Soaring], circa September 1900

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A pigeon moving directly from the observer oscillates very rapidly laterally, especially when moving slowly

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just before lighting. The wings are not drawn in to any perceptible extent first on one side and then on the other as would be the case if the bird were balancing by increasing or decreasing the area of either wing alternately. Moreover, the oscillations of lateral balance are so rapid that gravity alone could not possibly produce them. The bird certainly twists its wing tips so that the wind strikes one wing on top and the other on its lower side, thus by force changing the birds

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lateral position.

If a buzzard be soaring to leeward of the observer, at a distance of a thousand feet, and a height of about one hundred feet, the cross section of its wings will be a mere line when the bird is moving from the observer [*] but when it moves toward him the wings will appear broad [*]. This would indicate that its wings are always inclined upward, which seems contrary to reason.

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A bird when soaring does not seem to alternately rise and fall as some observers have thought. Any rising or falling is irregular and seems to be due to disturbances of fore-and-aft equilibrium produced by gusts. In light winds the birds seem to rise constantly without any downward turns.

A bird sailing quartering to the wind seems to always present its wings at a positive angle, although propulsion

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in such position seems unaccountable.

Birds cannot soar to the leeward of a descending slope unless high in the air.

Buzzards find it difficult to advance in the face of a wind blowing more than thirty miles per hour. Their soaring speed cannot be far from thirty miles.

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Citation: Diary entry, September 1900. Diary of Wilbur Wright, Papers of Wilbur and Orville Wright. Manuscript Division, Library of Congress.
Location: Manuscript Division, Library of Congress, Washington, D.C. 20540 USA

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Page Updated 14 October 2004
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