Andrew Ellicott (1754-1820) was the leading geodetic surveyor in the United States in
the early years of the Republic, and he aimed to produce surveys that compared favorably with
those done by the best Europeans in the field. In his words, the transit and equal altitude
instrument was "the most perfect, and best calculated for running straight lines." Moreover,
"when the different verifications are carefully attended to, [it] may safely be considered as
absolutely perfect."
Ellicott made this instrument himself, and used it to run the western boundary of New
York in 1789, the boundaries of the District of Columbia in the early 1790s, the southern
boundary of the United States in 1796-1800, and the boundary between Georgia and North
Carolina in 1811. Ellicott took this instrument with him to West Point, when he became
professor of mathematics at the U.S. Military Academy in 1813. A descendant, Andrew Ellicott
Douglass, deposited it with the Smithsonian in 1898.
This instrument is modeled on the transit and equal altitude instrument that had been
made by John Bird in London, purchased by Thomas Penn in 1763, and used by Mason and
Dixon for their survey of the boundary between the colonies of Maryland and Pennsylvania.
Ellicott had used this English instrument in 1784, when he was part of the team of American
surveyors who extended the Mason-Dixon line to the western edge of Pennsylvania.
Ref: Andrew Ellicott, "A Letter to Robert Patterson," Transactions of the American Philosophical Society 4 (1799): 32-51.
Andrew Ellicott, "An Account of the Apparatus used on the Boundary between the United States and His Catholic Majesty," Transactions of the American Philosophical Society 5 (1802): 204-208.
Silvio Bedini, "Andrew Ellicott, Surveyor of the Wilderness," Surveying and Mapping (June 1976): 113-135.
