The First Treatise on Photometry
Paris, Claude Jombert, 1729.

Essai d'Optique sur la gradation de la lumiere.

8vo. 8vo., (11) ff., 164 pp., (2) ff., with 3 folding copper-plate engravings. Bound in contemporary calf, spine with raised bands gilt; head and tail chipped, and joints cracked but sound. Bookseller’s ticket of Jounaux Jeune, Libraire on front end pastedown. Inconsequential toning and fingersoiling on title and scattered leaves, otherwise immaculate copy.

First edition of this important work on the measurement on light by “the father of photometry” (DSB) and the author’s first work on the subject.

“Bouguer’s 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.... In the latter part of the Essai, Bouguer published the second of his great optical discoveries, often called Bouguer’s law: 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 (l760) and, perhaps, because of the great rarity of copies of Bouguer’s Essai, is sometimes unjustifiably referred to as Lambert’s law.” – DSB II.343

Bouguer was the leading French authority on navigational science, and published widely on geodesy and hydrography. He was a member of the team of French scientists sent to Peru to measure an arc of the meridian near the equator.

* Norman 283; DSB II.343-44; NBG VI.910.

Price: $3,850.00

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