Pierre Bouguer (16.02.1698-15.08.1758) was a French scientist, one of the founders of photometry and a member of the Paris Academy of Sciences (1735). He was born in Le Croisic (Brittany). His research was in the fields of astronomy, geodesy, hydrography, gravimetry, naval architecture and optics. He was the first to establish the concept of the quantity of light and the principle of the gradation of light, and he constructed a photometer and developed methods of measuring luminous intensity. In 1729 he discovered the law of the attenuation of light in a medium, considered later by J. Lambert and A. Beer (the Bouguer-Lambert-Beer law). He invented the heliometer and the first practically usable photometer. He carried out (1729) the first experiments on measuring the quantity of heat received by the Earth's surface from the Sun's rays.