The polygons adopted were of 20 or more sides approximating to a circular form.
" Regular polyhedra " are such as have their faces all equal regular polygons, and all their solid angles equal; the term is usually restricted to the five forms in which the centre is singly enclosed, viz.
These have faces which are all regular polygons, but not all of the same kind, while all their solid angles are equal.
They bear a relation to the Platonic solids similar to the relation of " star polygons " to ordinary regular polygons, inasmuch as the centre is multiply enclosed in the former and singly in the latter.
- These solids are characterized by having all their angles equal and all their faces regular polygons, which are not all of the same species.