Arago: Exhibits


Polyhedrons and Globe Gore Projections

Special layouts for maps have been devised that, when cut out and assembled, make a polyhedron (many-sided figure) that approximates a globe. Cahill’s Butterfly is an attractive layout whether it is flat or assembled. Many projections can be applied to its eight facets. This example has curved sides that are best when applied and stretched onto an actual globe. If the map had straight edges, it would be assembled into an eight-sided polyhedron (an octahedron).

When cartographers make an earth globe, the map is originally printed flat, either as a series of pie-shaped sections or as a kind of curved picket fence. The map is then wetted down and stretched onto a preformed globe. The projection on Globe Gores is the lines of longitude drawn on a flat surface that, by trial and error, have been found to stretch to the correct position on the globe.

40c International Bar Association Conference single

Cahill’s Butterfly

7w World Conference of Teaching Profession single

Globe Gores