J. Green Pocket Compass (prismatic)

Description
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.
Location
Currently not on view
maker
Green, James
place made
United States: New York
Measurements
overall: 3 in; x 7.62 cm
ID Number
PH*314563
catalog number
314563
accession number
204612
See more items in
Medicine and Science: Physical Sciences
Measuring & Mapping
Surveying and Geodesy
Data Source
National Museum of American History, Kenneth E. Behring Center

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