Essai d'optique sur la gradation de la lumière.
Paris: Claude Jombert, 1729.
1st Edition. Hardcover. 12mo - over 6¾ - 7¾" tall. Very Good. Item #003602
12mo (165 x 99 mm). , 164,  pp. 3 folding engraved plates, woodcut initials and headpieces, 2 leaves with errata and printer's advert. Contemporary French mottled calf, spine with 5 raised bands gilt in compartments and gilt-lettered red morocco label, red-dyed edges, marbled endpapers (extremities rubbed, spine ends and corners worn). Provenance: W. Goumet (inscription on title-page). Text only very little browned, a few text corrections in ink. A near fine copy with the text printed on strong paper. ----
Norman 283; Honeyman 444; Macclesfield 399; DSB II, p.343. - FIRST EDITION. "Bouguer is regarded as the founder of photometry, the branch of optics concerned with measuring the intensity of light. His two most important contributions to the subject are contained in his Essai, the first part of which states his method of comparing the relative brightness of two lights" (Norman). A youthful prodigy who established himself early in life as the leading French authority on nautical matters, Bouguer merely dabbled in optics as a hobby. His interest in the measurement of light dates from c. 1721, when Jean-Jacques Dortous de Mairan proposed a problem that necessitated a knowledge of the relative amount of light from the sun at two altitudes. Bouguer succeeded in making such a measurement of the light from the full moon on 23 November 1725, by comparing it with that of a candle. His achievement was to see that the eye could be used, not as a meter but as a null indicator, i.e., to establish the equality of brightness of two adjacent surfaces. His second discovery concerned the transmission of light through transparent surfaces: "In a medium of uniform transparency the light remaining in a collimated beam is an exponential function of the length of its path in the medium. This law was restated by J.H. Lambert in his Photometria (1760) and, perhaps because of the great rarity of copies of Bouguer's Essai, is sometimes unjustifiably referred to as Lambert's law' (op. cit.)" (Norman). - Visit our website to see more images!
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