1698-1758

French hydrographer primarily interested in navigation and ship design but best known as the father of photometry. He formulated Bouguer's law—in a medium of uniform transparency the intensity of a collimated light beam decreases exponentially with the path length through the medium—often incorrectly attributed to Johann Lambert. Bouguer also invented the heliometer (1748) and photometer. He was a member of Charles La Condamine's celebrated Peru expedition (1735-44), which helped verify Newton's theory of gravitation.