# Geometric Models, L. Brill No. 99. Ser. 3 No. 9, Two Hyperboloids of Two Sheets

Description
In the nineteenth and early twentieth century, students studying technical subjects often learned about the representation of surfaces by equations in courses in solid analytic geometry. Schools in Europe, the United States, and Japan sometimes purchased models to illustrate such surfaces. These objects are part of series of models of quadric surfaces (surfaces of degree two) designed in 1878 by Rudolf Diesel, then a student at the technical high school in Munich. They were published by the firm of Ludwig Brill in Darmstadt. These examples were exhibited at the German Educational Exhibit at the Columbian Exposition held in Chicago in 1893, where they were purchased by Wesleyan University.
The plaster models show a hyperboloid of two sheets. The surface can be represented by the equation x2/a2 + y2/ b2 + z2/c2 = - 1. Sections parallel to the plane z=0 are ellipses. Sections by the planes x=0 and y=0, and planes parallel to these, are hyperbolas. Two metal rods hold together the two sheets of each model.
Grids of perpendicular lines of curvature are shown. A paper tag on one models reads: 99. Paper tags on both of them read: Zweischaliges Hyperboloid. (/) Verl. v. L. Brill. 3. Ser. Nr. 9.
Compare 1990.0571.07.
References:
Ludwig Brill, Catalog mathematischer Modelle. . ., Darmstadt: L. Brill, 1892, p. 7, 77.
Henry Burchard Fine and Henry Dallas Thompson, Coordinate Geometry, New York: Macmillan Company, 1931, pp. 240-241.
Gerard Fischer, Mathematical Models, Braunschweig / Wiesbaden: Friedr. Vieweg & Sohn, 1986, vol. I, p. 62, vol. II, pp.25-28.
Location
Currently not on view
1892
maker
L. Brill
Physical Description
metal (overall material)
plaster (overall material)
Measurements
each: 23.5 cm x 21 cm x 13 cm; 9 1/4 in x 8 9/32 in x 5 1/8 in
ID Number
1985.0112.072
catalog number
1985.0112.072
accession number
1985.0112
Credit Line