Mainka Conic (or Bifilar) Pendulum Seismograph

Francis Anthony Tondorf, S.J., director of the newly established seismological laboratory at Georgetown University, ordered several new seismographs in 1911. This one, which was advertised as “Dr. Mainka’s Small size Conic Pendulum,” was the first of its kind in the United States. It was designed by Carl Mainka, manager of the instrument department of the Imperial Station for earthquake investigations in Strasbourg, and manufactured by J. & A. Bosch, a firm that specialized in instruments for seismology and meteorology.
This seismograph stands 1.6 meters high and has two 130-kilogram masses, one for each horizontal motion. Registration occurs on a smoked paper mounted on a rotating aluminum cylinder. It came to the Smithsonian in 1961.
Ref: J. & A. Bosch, Seismographen (Strassburg, 1910), pp. 6-7.
C. Mainka, “Das bifilare Kegelpendel,” Mitteikugen der Philomathischen Gessellschaft in Elsasz-Lothringen 4 (1912): 633-667. This was reprinted as C. Mainka, Das bifilare Kegelpendel: (Instrumente für die Aufzeitnung von Erdbeben (Strasburg, 1913).
“G.U.’s Observatory Finest,” Washington Post (Feb. 27, 1911), p. 2.
Currently not on view
Object Name
date made
ca 1911
J. & A. Bosch
overall: 96 in x 48 in x 60 in; 243.84 cm x 121.92 cm x 152.4 cm
place made
France: Alsace, Strasbourg
ID Number
accession number
catalog number
Measuring & Mapping
Science & Mathematics
See more items in
Medicine and Science: Physical Sciences
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Georgetown University

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