Amsler is also credited with conceiving a design for a planimeter that restricted the movement of the end of the tracer arm opposite the tracer point to a straight line. The collections suggest that Americans were particularly interested in further developing linear planimeters, with examples patented by John Coffin, Edward Jones Willis, and Frederick R. Williams. Another linear planimeter sold by an American company and an instrument that does not fit any of the categories of planimeters are also included on this page.
In 1875, Danish mathematician and cavalry officer Holger Prytz came up with a final form of planimeter—the hatchet planimeter. It simply consists of a rod with a tracer point at one end and a chisel edge at the other. As the tracer goes around the drawing, the chisel makes a zigzag path. The product of the length of the path and the length of the rod gives the area of the drawing. The result, though, is not as accurate as those provided by more complex forms of planimeters. At present, no examples of this instrument are known to be among the mathematics collections.
"Planimeters - Linear" showing 1 items.
- This German silver linear planimeter is T-shaped. The base of the T has a measuring scale, which no longer can be read due to rust, and a metal wheel that slides up and down the scale when the planimeter is moved. The top of the T has a tracing point at one end. The other end fits into a metal groove screwed inside a rectangular mahogany case. Two clips fastened inside the case are for holding the paper marked with a steam engine indicator diagram, but the paper received with this object is held in place by four metal thumbtacks.
- The top of the case has a red and white inventory sticker marked: 1113 (/) 204-G-2. The sticker was presumably attached at Rutgers University, the donor of the object. A large white label glued inside the lid of the case is marked: THE • NEW • PLANIMETER (/) THE MECHANICAL SPECIALTIES MFG. CO. (/) 128 PURCHASE STREET, BOSTON, MASS. This label also has "directions for use." The inside bottom of the case is lined with blue paper. The paper held by thumbtacks contains a square drawn with pencil and marked: Begin here (/) Area (/) 4 sq. in. Above a circle drawn to the right of the square is marked: Circle is (/) 1 in. inside diam. (/) Area = Π / 4 = .785 sq. in. (/) Begin (/) here.
- The Mechanical Specialties Manufacturing Company was known for its "Arc" steam engine indicator, which it started to sell in 1888. The firm was apparently short-lived. By 1900, the Boston Journal of Commerce and Textile Industries was published from its address, and by 1918, the Boston Office Furniture Exchange was located at its address. Rolla Clinton Carpenter, associate professor of experimental engineering at Cornell, did describe the instrument in an 1893 textbook.
- References: The Mechanical Specialties Manufacturing Company, "A Treatise on the Arc Indicator," American Engineer 19, no. 10 (March 5, 1890): 107, and "Improvements in the Arc Indicator," American Engineer 20, no. 21 (November 22, 1890): 221–222; Rolla C. Carpenter, Experimental Engineering, 2nd ed. (New York: John Wiley & Sons, 1893), 36–37; Catalogue of Exhibitors in the United States Sections of the International Universal Exposition,, vol. 2 (Paris, 1900), 446; "Purchase St," Boston Register and Business Directory no. 83 (1918): 976.
- Currently not on view
- date made
- Mechanical Specialties Manufacturing Company
- ID Number
- catalog number
- accession number
- Data Source
- National Museum of American History, Kenneth E. Behring Center