BOUGUER , PIERRE

Bouguer, the son of a hydrographer and mathematician, was born in Le Croisic, France, and followed into his father's profession. He was a child prodigy and obtained a post as professor of hydrography at the remarkably early age of 15. The study of the problems associated with navigation and ship design was his chief interest. Bouguer took part in an extended expedition to Peru led by Charles de la Condamine to determine the length of a degree of the meridian near the equator. While on this expedition Bouguer also did a great deal of other valuable experimental work.

One of Bouguer's most successful inventions was the heliometer to measure the light of the Sun and other luminous bodies. Although it was not his chief interest the research for which Bouguer is now best remembered was on photometry. Here too he did much valuable experimental work and one of his major discoveries was of the law now named for him. This states that in a medium of uniform transparency the intensity of light remaining in a collimated beam decreases exponentially with the length of its path in the medium. The law is sometimes unjustly attributed to Johann Lambert. Bouguer's work in optics can be seen as the beginning of the science of atmospheric optics.