Mendenhall Gravity Pendulums

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.
Currently not on view
Object Name
gravity pendulums (Mendenhall 1/2 second)
date made
overall: 12 in; 30.48 cm
place made
United States: District of Columbia, Washington
ID Number
accession number
catalog number
Measuring & Mapping
U.S. Coast & Geodetic Survey
See more items in
Medicine and Science: Physical Sciences
Data Source
National Museum of American History, Kenneth E. Behring Center

Visitor Comments

Add a comment about this object

**Please read before submitting the form**

Have a comment or question about this object to share with the community? Please use the form below. Selected comments will appear on this page and may receive a museum response (but we can't promise). Please note that we generally cannot answer questions about the history, rarity, or value of your personal artifacts.

Have a question about anything else, or would you prefer a personal response? Please visit our FAQ or contact page.

Personal information will not be shared or result in unsolicited e-mail. See our privacy policy.

Enter the characters shown in the image.