Regular Octagon, Ross Surface Form

This is one of the models of plane figures (surface forms) designed by William Wallace Ross, a school superintendent and mathematics teacher in Fremont, Ohio. The flat wooden object is in the shape of a regular octagon. On the side of the model opposite from the label, an inscribed circle is indicated, as well as four lines joining opposite vertices of the octagon and meeting at the center of the circle. A paper tag attached to the model reads: OCTAGON.
In constructing his visual demonstration of the area of a circle, Ross built several regular polygons, and showed that they had areas equal to the sum of the area of triangles with height equal to the radius of an inscribed circle and sides equal to the sides of the polygons. In other words, the area of the regular polygon equaled half the perimeter of the polygon times the radius of the inscribed circle.
This is the example for an octagon. Compare 1985.0112.200 and 1985.0112.202. For the circle, see 1985.0112.203. For further information about Ross models, including references, see 1985.0112.191.
Currently not on view
Object Name
geometric model
date made
ca 1895
Ross, W. W.
Physical Description
wood (overall material)
overall: 1 cm x 14.8 cm x 15 cm; 13/32 in x 5 13/16 in x 5 29/32 in
place made
United States: Ohio, Fremont
ID Number
catalog number
accession number
Science & Mathematics
Arithmetic Teaching
See more items in
Medicine and Science: Mathematics
Arithmetic Teaching
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Wesleyan University
Additional Media

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