|Description||Brass compass with a variation arc on the north arm, and a level vial on the south arm. Signed "T. Whitney / Maker / Philadelphia" on compass face. The instrument is dated "1814" under socket. It is in its original condition, with the exception of the Jacob's Staff attachment screw, which was added at a later date.|
Philadelphia instrument-maker Thomas Whitney supplied many of the instruments used by eminent American surveyors, including Western explorers Meriwether Lewis and William Clark. This Whitney vernier compass incorporates two innovations to improve the accuracy of surveys. The level vial on the south arm of the instrument helped the surveyor keep the compass level, which made angle and compass readings more reliable. The vernier adjustment and mechanism on the north arm allowed surveyors to compensate compass readings for magnetic variation.
|Dimensions||H-8.438 L-14 Dia-6.063 inches|
|Credit line||American Philosophical Society|