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Transit and Equal Altitude Instrument

Transit and Equal Altitude Instrument

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The United States purchased the Louisiana Territory from France in 1803, paying $15 million for some 828,000 square miles. This Louisiana Purchase doubled the size of the country, and has often been called the greatest real estate deal ever made. Several months before the treaty was signed, President Thomas Jefferson appointed Isaac Briggs Surveyor General of what was then referred to as the Mississippi Territory. In preparation for this task, Briggs asked Andrew Ellicott for his transit and equal altitude instrument. When Ellicott refused to sell, Briggs turned to Henry Voigt (1738–1814), a German immigrant trained as a clock and watch maker. Briggs used this Voight instrument in 1804 to establish a prime meridian for the United States, running through Washington, D.C. He then took it to the new Territory and, since it had been purchased with federal funds, he left it there when he retired in 1807. The transit was transferred to the Surveyor General of Florida in the 1820s, placed in storage, and forgotten. It was transferred to the Smithsonian in 1891. The transit is marked "Henry Voigt Philadelphia."
Ref: Silvio Bedini, "The Case of the 'Worthless' Instruments," Professional Surveyor (October 1995): 49 50, and (November/December 1995): 61–62.
Currently not on view
Object Name
transit and equal altitude instrument
Voigt, Henry
telescope: 20 in; 50.8 cm
axis: 15 1/2 in; 39.37 cm
ID Number
accession number
catalog number
See more items in
Medicine and Science: Medicine
Surveying and Geodesy
Measuring & Mapping
Data Source
National Museum of American History
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