Essai d'Optique, sur la Gradation de la Lumiere.
Three folding engraved plates. 12 p.l. (the first leaf is a blank), 164,  pp. 8vo, cont. calf (upper joint cracked but firm, upper corners a bit worn), spine gilt, red morocco lettering piece on spine. Paris: C. Jombert, 1729.
First edition of the work which clearly established Bouguer as the discoverer of the first practical way of measuring light, as well as nearly all the photometric theory.
“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. He... More