Gift of Miss Frances Priestley of Northumberland, Pa., in 1958. USNM 315353. FIGURES 76, 77. RITTENHOUSE, BENJAMIN (1740-c. 1820). _Surveying Compass_, about 1796, of brass, 13-1/2 in. long over-all and 6-1/2 in. diameter. Supported on a tripod by means of a ball-and-socket joint and screw-tightening device. The name "A. Ellicott" is inscribed on one arm outside the bezel of the dial, and the name "B. Rittenhouse" is inscribed on the other arm. The number "10" is marked on the reverse of this instrument, which is listed in the _Journal of Andrew Ellicott_ as Item 9: "A Surveying Compass made by Mr. Benjamin Rittenhouse upon the newest and most approved plans." Gift of Henry B. Douglass of Newton, N.J., in 1934. USNM 310815. FIGURE 78. RITTENHOUSE, DAVID (1732-1796), Philadelphia, Pa. _Surveying Compass_, brass, over-all length 14 in., diameter 6-1/2 in., silvered dial marked with eight-pointed star indicating the cardinal and intermediate points, glazed. Inscribed "Rittenhouse, Philadelphia." Fitted with a ball-and-socket joint for mounting on a tripod, and complete with wooden field case. [Illustration: Figure 77.--Celestial globe made by W. & T. M. Bardin of London and used by Dr. Joseph Priestley. Diameter, 23 in. USNM 53254.] [Illustration: Figure 78.--Brass surveying compass made by Benjamin Rittenhouse for Andrew Ellicott and inscribed with both names. The instrument is described in _Journal of Andrew Ellicott_ (Philadelphia, 1803). USNM 310815.] Stated to have been used by General Washington for laying out the estate of Mount Vernon, according to family manuscripts. It was made by David Rittenhouse and presented by him to General Washington, who subsequently gave it to Capt. Samuel Duvall. A manuscript consisting of 14 letters relating to the surveying compass is filed in the U.S. National Museum (USNM 92542). The letters were written in 1851 and 1852 by George Washington Parke Custis, Anthony Kimmel, and other Washington descendants. Gift of Anthony Kimmel to the U.S. Government, and transferred to the U.S. National Museum in 1883. USNM 92538. FIGURE 79. _Zenith Sector_ for measuring the angle between a star at its zenith and the vertical. Made of brass, with focal length of 6 ft. and an aperture of 2-1/2 in. The original lens was made in London about 1780. The instrument was made in the old pattern with brass tube and mountings and a wooden supporting post. The tube is suspended by trunnions at the top and swings against a graduated arc extending north and south for measuring zenith distances in the meridian. It is adjusted in the vertical by a plumb line whose errors are eliminated by reversing the whole mounting about the supporting post. Constructed principally by David Rittenhouse, with some modifications by Andrew Ellicott.