Keuffel & Esser 4220 Amsler Style Polar Planimeter

This tarnished German silver instrument has two arms pivoted at one end. One arm has a tracer point and index marks for four ratios: 1 square D. (centimeters or meters, perhaps), 15 square inches, 10 square inches, and 10 square chains. A screw assembly adjusts the length of the tracer arm. A support for the tracer point prevents it from tearing the paper. Two numbers are stamped underneath the arm: 31, which appears to overstamp the number 33, and 690.

The other arm is jointed. A cylindrical weight may be placed in the end of that arm. Underneath the weight is marked: 35. The jointed part of the arm is marked: KEUFFEL & ESSER Co N.Y. Underneath the arm is stamped: 31. A carriage at the pivot holds a white plastic measuring wheel with vernier and a horizontal metal registering dial.

A mahogany case has dark blue velvet lining the supports. A leather pouch holds the weight. A paper chart for adjusting the tracer arm is held in the lid by black plastic edges and brass screws. The columns are labeled: Proportion, Adjustement [sic] on tracer-arm, and Value of unit of the Vernier. "Sq. units" is handwritten above the first entry in the Proportion column (1:1,000). The vernier entry for proportion 1:4,000 has been changed from 100 to 160 square meters.

Keuffel & Esser sold this planimeter as model 1102 from 1892 to 1901 and as model 4220 from 1901 to 1936. It sold for $28.00 in 1909 and for $45.50 in 1936. The serial number, 690, and lack of rectangular support for the joint in the weighted arm suggest that this example was made later than 1981.0348.01. Wesleyan University donated this planimeter to the Museum in 1984–1985 with a large collection of plaster and string mathematical models purchased in 1895 from the Darmstadt, Germany, firm of L. Brill.

This instrument was received at the Smithsonian in 1985 or 1985.

References: Catalogue of Keuffel & Esser, 33rd ed. (New York, 1909), 319; Catalogue of Keuffel & Esser, 38th ed. (New York, 1936), 336; Clark McCoy, "Collection of Pages from K&E Catalogs for the 4220 Family of Polar Planimeters," http://www.mccoys-kecatalogs.com/PlanimeterModels/ke4220family.htm.

Currently not on view