Troughton & Simms Theodolite

This is a standard theodolite as made by Troughton & Simms in the second quarter of the 19th century. The horizontal circle is silvered, graduated to 20 minutes, and read by two verniers with magnifiers to 20 seconds. The vertical arc is graduated and read in a similar manner. The scale "Diff. of Hypo. & Base" that appears on the back of the vertical arc is used to correlate the angle of elevation or depression with horizontal distances when surveying sloping ground. The instrument is marked "Troughton & Simms LONDON" and "No. 1" (which was probably added by a former owner).
Currently not on view
date made
Troughton and Simms
place made
United Kingdom: England, London
overall: 13 1/2 in; 34.29 cm
horizontal circle: 8 1/2 in; 21.59 cm
needle: 4 in; 10.16 cm
telescope: 13 7/8 in; 35.2425 cm
hanging level: 6 1/8 in; 15.5575 cm
overall: 16 3/8 in x 14 5/8 in x 18 9/16 in; 41.5925 cm x 37.1475 cm x 47.14875 cm
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catalog number
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Medicine and Science: Physical Sciences
Measuring & Mapping
Surveying and Geodesy
Data Source
National Museum of American History