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Francois Arago

Currency:USD Category:Collectibles / Autographs Start Price:NA Estimated At:300.00 - 500.00 USD
Francois Arago

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Auction Date:2017 May 10 @ 18:00 (UTC-05:00 : EST/CDT)
Location:236 Commercial St., Suite 100, Boston, Massachusetts, 02109, United States
ALS - Autograph Letter Signed
ANS - Autograph Note Signed
AQS - Autograph Quotation Signed
AMQS - Autograph Musical Quotation Signed
DS - Document Signed
FDC - First Day Cover
Inscribed - “Personalized”
ISP - Inscribed Signed Photograph
LS - Letter Signed
SP - Signed Photograph
TLS - Typed Letter Signed
French Catalan mathematician, physicist, astronomer, and politician (1786–1853). Handwritten manuscript in French, unsigned, four pages on two adjoining sheets, 7 x 9.5, no date. Arago writes on the topic of "Refraction terrestre [Earth refraction]." In part (translated): "In the computation of geodesic observations, it is supposed that the curve, concave towards the earth, which a ray of light traverses from one station to another, is a great arc of a circle. It is easy to see that in this hypothesis the effect of terrestrial refraction must be proportional to the angle formed between them by the vertical of the two stations, or, what is the same thing, to the extent of the arc of the great circle which joins them. The observation then has only to determine, that the fractional number by which this arc must be multiplied and that it is agreed to call the coefficient of refraction…The important role played by this coefficient in all Trigonometric leveling imposes on me the duty to record here units of value which M. Coraboeuf assigns." In very good condition, with areas of ink erosion and writing heavily showing through from opposing sides.