Coradi Polar Planimeter

Description
This instrument has two arms. The German silver tracer arm has a support for the tracer point and is evenly divided by tenths numbered from 10 to 37. Ten units are equivalent to 5mm. The tracer arm fits within a carriage of brass, painted black, that also holds a white plastic measuring wheel and vernier and a metal registering dial. The pole arm is made of brass painted black and is attached to the carriage. The end of the pole arm fits into a rectangular metal weight faced with brass painted black. The weight is marked: G. Coradi Zürich (/) No 759. The bottom of the weight is covered with paper. A cylindrical brass weight fits into a hole on top of the pole arm. The testing rule is missing.
A wooden case covered with black leather is lined with purple velvet. A paper printed chart glued inside the lid has columns in German 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 are handwritten. The date on the chart indicates the Coradi firm made serial number 759 on December 28, 1888.
Gottlieb Coradi (1847–1929) established a workshop in Zurich in 1880 and began making wheel and disc polar planimeters in the Amsler style soon thereafter. In 1894, he modified the design into the "compensating" polar planimeter; see MA*321777. Union College donated this instrument in 1964.
Reference: "People: Gottlieb Coradi," Waywiser, Harvard University Department of the History of Science, http://dssmhi1.fas.harvard.edu/emuseumdev/code/eMuseum.asp?lang=EN.
Location
Currently not on view
Object Name
planimeter
date made
1888
maker
Coradi, Gottlieb
Physical Description
german silver (overall material)
brass (overall material)
plastic (overall material)
wood (overall material)
leather (overall material)
paper (overall material)
Measurements
case: 5.2 cm x 38.5 cm x 5.2 cm; 2 1/16 in x 15 5/32 in x 2 1/16 in
place made
Schweiz: Zürich, Zurich
ID Number
MA*323707
catalog number
323707
accession number
252804
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
Gift of Union College
Additional Media

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