Allen Sextant

The "J. Allan, Baltimore" signature on this sextant refers to John Allen (b. 1786), an "optician and mathematical instrument maker" who appears in Baltimore city directories from 1810 to 1819. He was the son of James Allen, a noted instrument maker in London. And he boasted: "As all Instruments sold by me are graduated by my father’s improved self-correcting engine, for which the Society of Arts voted him their Gold Medal, on the 19th of May, 1810–they are warranted and will be kept in repair one year, gratis."
This sextant has a brass frame. The silvered scale is graduated every 20 minutes from -5° to +145° and read by vernier with tangent screw and magnifier to 1 second of arc. It belonged to the College of the Holy Cross in Worcester, Massachusetts.
Ref: Deborah J. Warner, "American Octants and Sextants: The Early Years," Rittenhouse 3 (1989): 86-112, on 89.
John Allen advertisement in the American & Commercial Daily Advertiser (June 12, 1816).
Currently not on view
Object Name
date made
Allen, John
radius: 7 in; 17.78 cm
place made
United States: Maryland, Baltimore
ID Number
accession number
catalog number
Measuring & Mapping
See more items in
Medicine and Science: Physical Sciences
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
College of the Holy Cross
Additional Media

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