Foucault, who employed a scale of equal bright and dark alternate parts; it was found to be proportional to the aperture and independent of the focal length.
An effort at a more direct mechanical process is embodied in the inventions of Foucault which are at present being developed in Germany and Belgium; in this process the glass is drawn from the molten bath in the shape of flat sheets, by the aid of a bar of iron, previously immersed in the glass, the glass receiving its form by being drawn through slots in large fire-bricks, and being kept in shape by rapid chilling produced by the action of air-blasts.
Foucault, he engaged in a series of investigations on the interference of light and heat.
After their deaths he lived for some time at Caen under the roof of Nicolas Foucault (1643-1721), the intendant of Caen, himself no mean archaeologist; and there he began the publication (12 vols., 1704-1717) of Les mille et une nuits, which excited immense interest during the time of its appearance, and is still the standard French translation.
JEAN BERNARD LEON FOUCAULT (1819-1868), French physicist, was the son of a publisher at Paris, where he was born on the 18th of September 1819.