Smithsonian - National Museum of American History, Behring Center

Physical Sciences Collection - Surveying and Geodesy

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Repeating Circle - click to enlarge

Repeating Circle - click to enlarge

Click photos to enlarge.

Repeating Circle

Catalogue number:

upper circle 17.5 inches diameter; circle at base 13.5 inches diameter; telescopes 24 inches long

This is one of two double repeating circles that Ferdinand Rudolph Hassler, the first Superintendent of the United States Coast Survey, ordered from Edward Troughton in London in 1812, and that was shipped in 1815. The large circle may be angled from vertical to horizontal to the opposite vertical position. It is graduated to 10 minutes, and read by four verniers and two magnifiers to single minutes. The upper image shows the original parts of this instrument that the Smithsonian received in 1955. The lower image shows the instrument as reconstructed in 1960.

Ref: F. R. Hassler, "Papers on Various Subjects Connected with the Survey of the Coast of the United States," Transactions of the American Philosophical Society 2 (1825): 232-420, on 315-320 and pl. VII.

"The Repeating Circle Without Reflection, as made by Troughton," in The Cyclopaedia: or, Universal Dictionary of Arts, Sciences, and Literature, edited by Abraham Rees (London, 1819), Vol. VII, Art "Circle."

Further Information:

Repeating Circle
Troughton & Simms