Mendenhall Gravity Pendulums

Description
These are some of the earliest examples of the pendulums that Thomas C. Mendenhall designed soon after he became superintendent of the U.S. Coast and Geodetic Survey. One is marked "U.S.C. & G.S. A1"; the second "U.S.C. & G.S. A2"; and the third "U.S.C.& G.S. A3." Each is also stamped with the date "1891." The dummy pendulum (presumably marked "A0") is missing.
Each pendulum is made of a copper-aluminum alloy, with a flat stem supporting a lenticular bob. Each has a period of swing of nearly ½ second, so that a coincidence between the pendulum and a chronometer would occur every 5 or 6 minutes. These pendulums are similar to those designed by von Sterneck of Austria in the late 1880s, and widely used in Europe. Mendenhall, however, reversed the mode of support, putting the plane surface on the pendulum, and the knife edge on the corresponding stand. This design, he claimed, made the pendulums less liable to accidental injury.
The Coast and Geodetic Survey produced many sets of Mendenhall apparatus, and used them until the 1930s. It transferred this example to the Smithsonian in 1955.
Ref: Victor Lenzen and Robert Multhauf, "Development of Gravity Pendulums in the 19th Century," United States National Museum Bulletin 240 (1965): 301-348.
C. H. Swick, Modern Methods of Measuring the Intensity of Gravity (Washington, D.C.: United States Coast and Geodetic Survey, 1921).
T. C. Mendenhall, "Determination of Gravity with the New Half-Second Pendulum," Report of the Superintendent of the U.S. Coast and Geodetic Survey for 1890-91, part 2, pp. 503-564.
Location
Currently not on view
date made
1891
place made
United States: District of Columbia, Washington
Measurements
overall: 12 in; 30.48 cm
overall: 6 5/8 in x 19 in x 9 3/4 in; 16.8275 cm x 48.26 cm x 24.765 cm
ID Number
PH*314639
accession number
208213
catalog number
314639
subject
U.S. Coast & Geodetic Survey
See more items in
Medicine and Science: Physical Sciences
Measuring & Mapping
Data Source
National Museum of American History, Kenneth E. Behring Center

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