BOUGUER, Pierre.

Inquire · Offered by Peter Harrington

Essai d'optique, sur la gradation de la lumière. First edition of the earliest work on photometry, in which Bouguer first sets out the method for measuring the intensity of light. The treatise also presents the earliest photometrical calculations, which compute the luminosity of a star as a function of its distance from earth, and compare the luminosity of the sun and the full moon. It is the first known demonstration of the Beer-Lambert Law."The distances of two sources that illuminated a split visual field were changed until the field was equally bright; the ratio of the square of the distances gave the relative luminous power of the two sources" (Bibliotheca Opticoria). He also describes the calculation of light intensity with reference to material reflection, absorption, and translucence. "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" (DSB).Pierre Bouguer (1698-1758) took over the professorship of hydrography from his father at Le Criosic in Brittany aged only 16. His academic career contributed significantly to improvements in the construction of ship masts and stability, particularly the publication of his La Traité du Navire (1746), earning him the title "the father of naval architecture".

Found via Rare Books Intel, a search across rare-book dealers, auction houses and marketplaces worldwide.