Prototype for Willis Two-Wheeled Planimeter

Even after the apparent commercial success of his "improved planimeter," Edward Jones Willis (1866–1941), a steam and electrical engineer from Richmond, Va., continued to experiment with planimeter designs. On January 17, 1922, he received a patent for a planimeter that had the measuring wheel on a spindle instead of a wheeled carriage, and had a magnifying glass attachment.
Willis noted that date on this instrument, but it bears little resemblance to the patent drawings. A brass arm with metal tracers at both ends moves perpendicularly to a brass frame. The arm is evenly divided in increments marked 99, 88, 77, 66, 55, 44, and 33. A metal bar at the front of the frame has a brass slide. Next are two brass wheels on spindles fastened to a brass plate in the center. At the back is a wooden triangular ruler with six scales on white celluloid. These scales divide the inch into 100, 50, 60, 30, 80, and 40 parts. The ruler is marked: J. L. ROBERTSON & SONS, N.Y. Presumably, the ruler came from one of the Improved Willis Planimeters made by Robertson between 1896 and the 1910s. The back of the frame is marked: E. J. WILLIS (/) RICHMOND, VA. (/) PAT. APL'D FOR.
A metal rod has rectangular brass ends. A triangular metal plate has brass bolts holding prickers and a brass post that holds one end of the rod. A small brass clamp is loose in the crudely made wooden case, which appears to be made from a shipping crate. Handwriting on the inside of the lid reads: Edward J. Willis (/) Room 119 Mutual Bldng (/) P.O. Box 416 Richmond Va (/) Jany 17h 1922 (/) WILLIS TWO WHEEL PLANIMETER. There is no record of a patent that applies specifically to this apparent prototype.
For information on Willis's earlier patents and planimeters, see 1994.0356.02, MA*324247, MA*323703, and MA*323704. At the same time that Willis worked on his later planimeters, he became interested in celestial navigation and published two textbooks on the subject. He invented a navigating machine and an altitude-azimuth instrument in the 1930s.
References: Edward J. Willis, "Planimeter" (U.S. Patent 1,404,180 issued January 17, 1922); Hyman A. Schwartz, "The Willis Planimeter," Rittenhouse 7, no. 2 (1993): 60–64; Willem F.J. Mörzer Bruyns, "The Willis Navigating Machine: A Forgotten Invention," Rittenhouse 14 (June 2000): 13–25.
Currently not on view
date made
Willis, Edward Jones
place made
United States: Virginia, Richmond
Physical Description
brass (overall material)
steel (overall material)
wood (overall material)
celluloid (overall material)
case: 5.2 cm x 31 cm x 10 cm; 2 1/16 in x 12 7/32 in x 3 15/16 in
ID Number
catalog number
accession number
Credit Line
Gift of John H. White, Jr.
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Data Source
National Museum of American History, Kenneth E. Behring Center


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