Pocket Compass (prismatic)


This compass is similar to the one for which Charles Schmalcalder, a London instrument maker, obtained a British patent in 1812. It is designed so that a surveyor can read the card while sighting a distant object. It has a tall folding sight at north, and at south, a shorter sight with a prismatic eyepiece at its base. The floating card is colored bright green; the numbers around its edge read correctly when seen through the prismatic eyepiece.

This example is marked "U. S. ENGINEERS" and "J. Green N. Y." The U. S. Weather Bureau transferred it to the Smithsonian in 1954. James Green was born in England in 1808, moved to the United States around 1832, and opened an instrument shop in Baltimore. He opened a second shop in New York in the early 1840s, and retired in 1885.

Maker: Green, James

Location: Currently not on view

Place Made: United States: New York

See more items in: Medicine and Science: Physical Sciences, Surveying and Geodesy, Measuring & Mapping


Exhibition Location:

Credit Line: U.S. Department of Commerce, U.S. Weather Bureau

Data Source: National Museum of American History

Id Number: PH.314563Catalog Number: 314563Accession Number: 204612

Object Name: Pocket Compass (Prismatic)

Measurements: overall: 3 in; x 7.62 cmoverall: 13/16 in x 4 in x 3 in; 2.06375 cm x 10.16 cm x 7.62 cm

Guid: http://n2t.net/ark:/65665/ng49ca746a5-9adc-704b-e053-15f76fa0b4fa

Record Id: nmah_761555

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