Smithsonian - National Museum of American History, Behring Center

Physical Sciences Collection - Surveying and Geodesy

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Altitude and Azimuth Instrument
Chain, Tape and Base Bar
Compass, Pocket
Compass, Railroad
Compass, Solar
Compass, Surveyor's
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Electromagnetic Distance Measurement (EDM)
Holland Circle
Range Finder
Repeating Circle
Transit and Equal Altitude
Transit, Geodetic
Universal Instrument
Vertical Circle
Zenith Telescope


Railroad Compass

The history of this type of instrument begins with the "Improved Surveying Compass" described in William J. Young’s 1830 patent application. The patent was granted in 1832, withdrawn for technical reasons, and granted again in 1834. Young designed this instrument so that surveyors could measure horizontal angles either with or without reference to magnetic north. The design proved to be especially useful for railroad surveys, and most examples were sold for that purpose. An advertisement in the American Railroad Journal for March 23, 1833, carried several testimonials. One from a civil engineer stated: "Having for the last two years made constant use of Mr. Young’s ‘Patent Improved Compass,’ I can safely say I believe it to be much superior to any other instrument of the kind, now in use, and as such most cheerfully recommend it to Engineers and Surveyors." The term "Railroad Compass" came into use after the expiration of Young’s patent in the mid-1840s.

Young’s patent describes a compass with two plates of nearly equal diameter. The upper plate carries the sights, ring, and needle, as in an ordinary compass. It also has an opening through which is visible a small portion of the finely graduated circle on the lower plate, and a vernier for subdividing the divisions of that lower circle. The two plates are moved relative to one another by tangent screw, by rack and pinion, or "by any other method that may be preferred." By replacing the vertical sights with a telescope, Young transformed the Improved Compass into the Surveyor’s Transit.