Graphometer

Catalogue number:
1994.0377.01

Inscriptions:
"J. M. LILLEY'S PATENT NOV. 10 1857" and "F. W. & R. KING BALTIMORE 26"

Dimensions:
14.5 inches long, 8 inches wide, 8 inches high

Discussion:
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.

Further Information:

Graphometer