A cathetometer is an upright ruler equipped with a telescope that is designed to measure the vertical difference between two points with great accuracy. The form was introduced in Paris around 1815 and the name around 1847.
This example was made by William Gaertner, a German immigrant who, in 1896, established a shop in Chicago for manufacturing astronomical and other instruments of precision. A quarter century later Gaertner would be honored for “having emancipated American educational and scientific institutions from their dependence on foreign made scientific instruments.”
This is one of Gaertner’s heaviest and most accurate cathetometers. It was also one of the most expensive, costing $400 when new. The signature—WM GAERTNER & CO. CHICAGO, USA—indicates that it was made between 1896 when the firm began in business under that name, and 1923 when it became the Gaertner Scientific Corp.
The silvered scale is graduated to 0.05 inches and read by vernier to 0.001 inches; it is also graduated in millimeters and read by vernier to tenths.
Ref: D. J. Warner, “Cathetometers and Precision Measurement: The History of an Upright Ruler,” Rittenhouse 7 (1993): 65–75.
Wm. Gaertner & Co., Instruments of Precision (Chicago, 1919), pp. 28–29.
Currently not on view
Object Name
date made
1896 - 1923
Wm. Gaertner & Co.
Physical Description
iron (overall material)
brass (overall material)
overall: 79 in x 34 in x 34 in; 200.66 cm x 86.36 cm x 86.36 cm
place made
United States: Illinois, Chicago
ID Number
catalog number
accession number
Science & Mathematics
See more items in
Medicine and Science: Physical Sciences
Data Source
National Museum of American History, Kenneth E. Behring Center

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