Graphometer

Like a standard graphometer, this one has a graduated semicircle, a pair of fixed sights, and an alidade with sights at either end. The semicircle is graduated to 30 minutes, and read by verniers at either end of the alidade to two minutes. There is a trough compass, two level vials, and an outkeeper. Unlike a standard graphometer, however, the fixed sights here are attached to the underside side of the plate, the alidade is graduated and equipped with a secondary rule and quadrant, and the face is covered with a grid.

The inscriptions read "J. M. LILLEY'S PATENT NOV. 10 1857" and "F. W. & R. KING BALTIMORE 26." The title of the patent (#18,608) granted to James M. Lilley (1802-1875) of Greenville, Va., on November 10, 1857, describes an "Improved Instrument for Surveying and Calculating Areas." The text refers to a new and improved "Compass" that is "intended to facilitate calculation of oblique-angled trigonometry and finding the area of triangles." The patent drawing refers to an "Altitude Instrument."

F. W. & R. King were in business in Baltimore from 1849 to 1875, selling camera equipment and instruments for surveyors and engineers. The Department of Civil Engineering of the University of Missouri at Rolla donated this instrument to the Smithsonian in 1994.

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