The polygons adopted were of 20 or more sides approximating to a circular form.
These have faces which are all regular polygons, but not all of the same kind, while all their solid angles are equal.
" 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.
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.