Sculpture, even more than painting, is based on geometry. The colossi of Egypt, the bas-reliefs of Assyria, the figured pediments and metopes of the temples of Greece, the carved tombs of Revenna, the Della Robbia lunettes, the sculptured tympani of Gothic church portals, all alike lend themselves in greater or less degree to a geometrical synopsis (Illustration 57). Whenever sculpture suffered divorce from architecture the geometrical element became less prominent, doubtless because of all the arts architecture is the most clearly and closely related to geometry. Indeed, it may be said that architecture is geometry made visible, in the same sense that music is number made audible. A building is an aggregation of the commonest geometrical forms: parallelograms, prisms, pyramids and cones--the cylinder appearing in the column, and the hemisphere in the dome. The plans likewise of the world's famous buildings reduced to their simplest expression are discovered to resolve themselves into a few simple geometrical figures. (Illustration 58). This is the "bed rock" of all excellent design. [Illustration 60: EGYPTIAN; GREEK; ROMAN; MEDIÆVAL] [Illustration 61: JEFFERSON'S PEN SKETCH FOR THE ROTUNDA OF THE UNIVERSITY OF VIRGINIA] [Illustration 62: APPLICATION OF THE EQUILATERAL TRIANGLE TO THE ERECHTHEUM AT ATHENS] [Illustration 63] [Illustration 64: THE EQUILATERAL TRIANGLE IN ROMAN ARCHITECTURE] But architecture is geometrical in another and a higher sense than this. Emerson says: "The pleasure a palace or a temple gives the eye is that an order and a method has been communicated to stones, so that they speak and geometrize, become tender or sublime with expression." All truly great and beautiful works of architecture from the Egyptian pyramids to the cathedrals of Ile-de-France--are harmoniously proportioned, their principal and subsidiary masses being related, sometimes obviously, more often obscurely, to certain symmetrical figures of geometry, which though invisible to the sight and not consciously present in the mind of the beholder, yet perform the important function of coördinating the entire fabric into one easily remembered whole. Upon some such principle is surely founded what Symonds calls "that severe and lofty art of composition which seeks the highest beauty of design in architectural harmony supreme, above the melodies of gracefulness of detail." [Illustration 65: THE EQUILATERAL TRIANGLE IN ITALIAN ARCHITECTURE] [Illustration 66: THE HEXAGRAM IN GOTHIC ARCHITECTURE]