Coradi Compensating Polar Planimeter Sold by Keuffel & Esser (Model 4240)

Description
This instrument has two arms. The first arm is 9" long. Made of German silver, it has a brass and steel tracer point. The arm is evenly divided into tenths and numbered from 5 to 38. It fits into a brass carriage, painted black, which also holds a white plastic measuring wheel, vernier, and registering dial. Screws on the carriage adjust the length of the tracer arm. The carriage is marked: No 22241.
An 8" brass (painted black) pole arm fits into a hole in the carriage. A cylindrical brass weight is attached to the other end. The arm is marked: G. Coradi, Zürich Switzerland Keuffel & Esser Co New York. An oblong steel testing plate is marked for 0", 1", 2", and 3". It is also marked: G. Coradi Zürich.
A wooden case covered with black leather is lined with purple velvet. A printed paper chart is pasted inside the case. The chart has columns for Scales, Position of the vernier on the tracer bar, Value of the unit of the vernier on the measuring roller, and Constant. The values in the Position and Constant columns are handwritten in the same hand that indicates the Coradi firm manufactured this planimeter with serial number 22,241 on July 15, 1914. Keuffel & Esser stamped the chart with its model number, 4240.
Gottlieb Coradi (1847–1929) began to make wheel and disc polar planimeters in the early 1880s. In 1894 he made the pole arm higher than the tracer arm and connected the arms with a ball joint. This "compensating" planimeter could trace in both the clockwise and counterclockwise directions, preventing errors introduced by planimeters made in the Amsler style. In 1901 K&E began selling Coradi's compensating planimeter for $36.00. In 1936 the firm began offering the planimeter under the company's Paragon brand name and charged $49.00. K&E stopped selling the instrument in 1939. The Interstate Commerce Commission transferred this example to the Smithsonian in 1963. ID number 1977.0112.02 is an instruction manual.
References: Peggy Aldrich Kidwell, "Planimeter," in Instruments of Science: An Historical Encyclopedia, ed. Robert Bud and Deborah Jean Warner (London: Garland Publishing, 1998), 467–469; "The Lang-Coradi Planimeter," in Olaus Henrici, "On Planimeters," in Report of the Sixty-fourth Meeting of the British Association for the Advancement of Science (London, 1894), 496–523, on 515; Clark McCoy, "Collection of Pages from K&E Catalogs for the 4240 Family of Polar Planimeters," http://www.mccoys-kecatalogs.com/PlanimeterModels/ke4240family.htm; Catalogue of Keuffel & Esser, 33rd ed. (New York, 1909), 323; Catalogue of Keuffel & Esser, 38th ed. (New York, 1936), 256.
Location
Currently not on view
Object Name
planimeter
date made
1914
distributor
Keuffel & Esser Co.
maker
Coradi, Gottlieb
Physical Description
steel (overall material)
brass (overall material)
plastic (overall material)
wood (overall material)
leather (overall material)
fabric (overall material)
paper (overall material)
Measurements
case: 4 cm x 25 cm x 8.7 cm; 1 9/16 in x 9 27/32 in x 3 7/16 in
place made
Schweiz: Zürich, Zurich
ID Number
MA*321777
catalog number
321777
accession number
246883
subject
Science & Mathematics
Mathematics
Engineering
Planimeters
See more items in
Medicine and Science: Mathematics
Planimeters
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Transfer from the Interstate Commerce Commission
Additional Media

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