"J. M. LILLEY'S PATENT NOV. 10 1857" and "F. W. & R. KING BALTIMORE 26"
14.5 inches long, 8 inches wide, 8 inches high
Like a standard graphometer, this instrument has a graduated semi-circle, a pair of fixed
sights, and an alidade with sights at either end. The semi-circle is graduated to 30 minutes, and
read by verniers at either end of the alidade to 2 minutes. There is a trough compass, 2 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 title of the patent (#18,608) granted to James M. Lilley of Greenville, Virginia, on November 10, 1857 describes an "Improved Instrument for Surveying and Calculating Areas." The text of the patent refers to a new and improved "Compass" that is "intended to facilitate
calculation of oblique-angled trigonometry and finding the area of triangles." And the patent
drawing refers to an "Altitude Instrument." F. W. & R. King were in business in Baltimore
during the period 1849-1875, 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.