Regular Bodies are of two kinds, the one have Surfaces, that are either Spherical, Ellyptical, or Curved in some other Way; The other have several Sides or Faces, which form so many several Surfaces, separated from each other by Angles; and these Bodies are either regular or irregular. Now a Spherical or an Oval Body, will always have a Relievo, and appear rais'd from its Ground, even though both the Gaound and the Body have the same Colour; and the same thing may be observed of Poligons, or Bodies of many sides: The reason is, that they are naturally dispos'd to produce Shadows on one of their sides, which is what a bare, flat Surface is incapable of.