Pool Surveyor's Vernier Compass

This compass, marked "H.M. Pool, EASTON, MASS.," has a variation arc on the south arm that extends 15 degrees either way. The vernier is moved by a tangent screw, also on the south arm, and reads to 4 minutes. Two two level vials are on the north arm.
Horace Minot Pool (1803-1878) began working with his older brother John in the mid-1820s, making a variety of mathematical instruments. In 1841, when John withdrew from the firm, H. M. Pool continued on his own. The 1860 Federal Census of Industry reports that, with the help of six male hands, Pool had an annual production rate of 55 compasses worth $1,650, 18 transits worth $1800, 2 theodolites worth $550, and miscellaneous items worth another $500. Pool showed two "circumferentors" at the Massachusetts Charitable Mechanic Association fair of 1850, and his surveying instruments won a silver medal at that association's fair in 1874.
Ref: Donald and Anne Wing, "The Pool Family of Easton, Massachusetts," Rittenhouse 4 (1990): 118-126.
Currently not on view
Object Name
compass (surveyor's vernier)
Pool, Horace Minot
overall length: 15 in; 38.1 cm
needle: 5 1/8 in; 13.0175 cm
place made
United States: Massachusetts, Easton
ID Number
catalog number
accession number
Measuring & Mapping
Surveying and Geodesy
See more items in
Medicine and Science: Physical Sciences
Surveying and Geodesy
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Colby College
Additional Media

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