Graham, George, 1674?–1751, English instrument maker. A clockmaker by trade, Graham designed clocks and watches that earned him membership in the Royal Society and were still manufactured into the present century. In 1725 he built a very accurate 8-ft (2.4-m) quadrant for the royal astronomer, Edmund Halley, at Greenwich; it was widely copied. His most important invention remains the micrometer screw, which enabled him to build zenith sections and calipers of unprecedented precision. Graham is buried in Westminster Abbey.