Smithsonian - National Museum of American History, Behring Center

Physical Sciences Collection - Surveying and Geodesy

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Surveyor's Vernier Compass - click to enlarge

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Surveyor's Vernier Compass

Catalogue number:

"Wm. J. Young Maker Philadelphia"

length 15 inches; needle 5.625 inches

This compass has two notable features. One is that the variation arc and vernier mechanism are located on the compass face, under glass and protected from harm. A similar design appears in the drawing accompanying William J. Young's 1830 patent application for an "Improved Surveying Compass." That instrument, however, had a full divided circle rather than a small variation arc. The other feature of this compass--a dark face and a silvered needle ring--was also described in Young's patent, and seems to be found on all Young compasses with a needle 5 inches or longer. The Journal of the Franklin Institute 10 (1832): 34, explained that this improvement of Young's "consists in colouring the surface of the compass plate green, or bronzing it, instead of silvering it in the usual way, thereby relieving the eye from the unpleasant and injurious effects of the white plate. A narrow silvered rim surrounds the bronzed surface, giving a distinct view of the needle point."

This compass belonged to Gettysburg College, and dates from the late 1840s or early 1850s, after the expiration of Young's patent, and before Young began placing serial numbers on his instruments. The variation arc extends 20 some degrees either way, and is graduated to 30 minutes. The vernier is moved by rack and pinion located on the south arm and hidden under a brass plate, and reads to single minutes. There is an outkeeper and a level vial (now missing) on the north arm.

Further Information:

Surveyor's Compass