Smithsonian - National Museum of American History, Behring Center

Physical Sciences Collection - Surveying and Geodesy

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Catalogue number:

"U. S. C. & G. S. No. 308"

height 20 inches; horizontal circle 9 inches diameter; vertical circle 6 inches diameter; telescope 12 inches long; striding level with 4 inch vial


This theodolite was designed in 1924 by Douglas L. Parkhurst, chief of the Instrument Division of the United States Coast and Geodetic Survey. It was made by August Heim, an instrument maker who worked with Parkhurst and contributed several ideas to its development. It was completed in July 1927. The horizontal circle is silvered, graduated to 5 minutes, and read by two micrometer microscopes to single seconds.

Aiming to produce an instrument suitable for first order geodetic work, Parkhurst was concerned that there be "no appreciable change in the fit of the vertical axis bearing due to changes in temperature," and no frictional drag between the telescope alidade and the graduated circle. Moreover, "The entire design must be made with a view to ruggedness and speed of manipulation and to provide for simple and easy adjustment under field conditions." By 1928 he could boast that "field tests" had proven his theodolite "to be one of the most accurate, rapid and durable instruments" that the Survey had ever used.

Ref: Douglas L. Parkhurst, "A New First Order Theodolite," Journal of the Franklin Institute (1928): 624-629.

Douglas L. Parkhurst, "Unusual Design in New Theodolite," Engineering News-Record 101 (1928): 806-808.

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