Smithsonian - National Museum of American History, Behring Center

 
Physical Sciences Collection - Surveying and Geodesy

Browse Makers | Browse Instruments | Index

Back
 

Surveyor's Vernier Compass - click to enlarge

Surveyor's Vernier Compass - click to enlarge

Click photos to enlarge.

Surveyor's Vernier Compass

Catalogue number:
PH*328411

Inscriptions:
"W. & L. E. Gurley Troy, N.Y."

Dimensions:
length 15.5 inches; needle 6 inches

Discussion:
Since the signature-with its v-shaped trenches and lines of varying weight-was clearly engraved by hand, the compass was made between 1852 when W. & L. E. Gurley began in business, and before the middle of 1876 when their new engraving machine was up and running. The variation arc on the south arm extends 20 degrees either way; the vernier is moved by a tangent screw, also on the south arm, and reads to 2 minutes. There are two level vials on the north arm. The side of one vertical sight is graduated to half degrees, for determining angles of elevation or depression. In 1871, a compass of this size and design cost $50.

Ref: W. & L. E. Gurley, A Manual of the Principal Instruments Used in American Engineering and Surveying (Troy, N.Y., 1871), pp. 23-27.

Further Information:

Gurley
Surveyor's Compass

Back