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Detail of the compass face
 

Surveyor's Vernier Compass
1798-1901

Drawing the line between Canada and the United States
Except for the original 13 colonies, the lands of the United States were surveyed prior to settlement. This policy began with the Land Ordinance of 1785, and most of the surveys were conducted with vernier compasses of the sort shown here. The signature on this compass--"RITENHOUSE & EVANS"-- refers to Benjamin Rittenhouse and his junior partner, Benjamin Evans, who worked together in Pennsylvania, in the years 1798 - 1801. The vernier mechanism enables the surveyor to compensate for local magnetic variation. This feature was introduced to David Rittenhouse, and early instruments of this sort were often referred to as Rittenhouse compasses. The original owner of the compass was John Johnson who served as Surveyor General of Vermont, and as an American commissioner for the survey of the boundry between Maine and Canada in the years 1817-1820. There is no evidence, however, to suggest that Mr. Johnson used this particular instrument for this purpose.

Notes
John Johnson (1740-1825)
Benjamin Rittenhouse (1740-1825)
David Rittenhouse (1732-1796)
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