Theodolite

Description
This theodolite was designed in 1924 by Douglas L. Parkhurst, chief of the Instrument Division of the U. S. 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..The signature reads "U. S. C. & G. S. No. 308."
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, he wrote, "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 Parkhurst 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.
Measurements
overall: 20 in; 50.8 cm
horizontal circle: 9 in; 22.86 cm
vertical circle: 6 in; 15.24 cm
telescope: 12 in; 30.48 cm
striding level vial: 4 in; 10.16 cm
ID Number
PH*314801
accession number
206598
catalog number
314801
See more items in
Medicine and Science: Physical Sciences
Measuring & Mapping
Surveying and Geodesy
Data Source
National Museum of American History, Kenneth E. Behring Center

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