Measuring & Mapping
Where, how far, and how much? People have invented an astonishing array of devices to answer seemingly simple questions like these. Measuring and mapping objects in the Museum's collections include the instruments of the famous—Thomas Jefferson's thermometer and a pocket compass used by Meriwether Lewis and William Clark on their expedition across the American West. A timing device was part of the pioneering motion studies of Eadweard Muybridge in the late 1800s. Time measurement is represented in clocks from simple sundials to precise chronometers for mapping, surveying, and finding longitude. Everyday objects tell part of the story, too, from tape measures and electrical meters to more than 300 scales to measure food and drink. Maps of many kinds fill out the collections, from railroad surveys to star charts.
"Measuring & Mapping - Overview" showing 1 items.
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- 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.
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- National Museum of American History, Kenneth E. Behring Center