Planimeter, Parallel Bar Type

This instrument consists of 12 flat parallel metal rods screwed at each end to somewhat wider parallel rods. The rods are equally spaced, except for the first and last, which are only half as far apart as the others. The device was designed for locating ordinates on a steam-engine indicator diagram that should be measured and multiplied by the length of the diagram to give a rough estimate of the area under the curve. This object was owned by the renowned American designer of steam engines, Erasmus Darwin Leavitt Jr. (1836–1916), and donated by his granddaughter, Margaret van D. Rice.
Reference: N. Hawkins, Hawkins' Indicator Catechism (New York: Theo. Audel & Co., 1903), 107–110.
Currently not on view
Object Name
planimeter, rectangular
date made
late 19th century
Physical Description
metal (overall material)
overall: .3 cm x 16.1 cm x 13.5 cm; 1/8 in x 6 11/32 in x 5 5/16 in
ID Number
catalog number
accession number
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Margaret van D. Rice

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