John Locke, a physician and scientist in Cincinnati, Ohio, described a reflecting level at a meeting of American geologists and naturalists in 1842, and obtained a patent (#7,477) in 1850. Locke's instrument consists of a small spirit level on a brass sighting tube, with a small diagonal reflector so arranged that the user can see the bubble and a distant sight at the same time. This simple and perhaps homemade Locke level belonged to the Anglo-American physician and scientist, William Draper (1811-1882), or one of his descendants.
