ALS in French, signed “G. Eiffel,” two pages on two adjoining sheets, 5.25 x 8.25, September 5, 1909. Letter to “My dear Captain,” in full (translated): "I have received your friendly letter dated August 26 and the note that was included in it for which I thank you. Would you let me wait until I get back in Paris to answer it, my vacation is not permitting me to do it with the reflection that it contains, all the more that the question is touchy and that by abandoning material prone idea you reduce it to a short of mathematical expression. If I start back my fall [free fall apparatus] experiments presently abandoned for another series of experiments made with a fan, I would be rather prepared to equip, as you suggest to me, the fix part of a parachute, which following my idea would allow to increase its weight in comparison to the mobile part without increasing kinetic power, by reducing speed: I would only fear that the wind would disrupt experiments too often.” In very good to fine condition, with several small holes affecting nothing, and irregular toning to the first page.
Eiffel actually began his studies in aerodynamics on the Eiffel Tower, conducting drop tests of various objects from the 377–foot high second platform. In 1909 he expanded this research by building a wind tunnel nearby, where he used fans driven by electric motors to create wind. Known as the ‘Eiffel-type’ wind tunnel, the designs he developed are still in use today. An excellent letter related to Eiffel’s lesser-known contributions to science and technology. Pre-certified PSA/DNA.
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