A moulding is the architect's means of drawing a line on his building. If he desires to mark on the exterior the position of an internal floor, or in any other way to suggest a division into storeys, a moulded string-course is introduced. If he wishes to add richness and play of light and shade to the sides of an important arch, he introduces a series of mouldings, the profile of which has been designed to form lights and shadows such as will answer his purpose. If again he desires to throw out a projection and to give the idea of its being properly supported, he places under his projection a corbel of mouldings which are of strong as well as pleasing form, so as to convey to the eye the notion of support. Mouldings, it can be understood, differ in both size and profile, according to the purpose which they are required to serve, the distance from the spectator at which they are fixed, and the material out of which they are formed. In the Gothic periods they also differed according to the date at which they were executed. [Illustration: FIG. 26.--EARLY ARCH IN RECEDING PLANES.] [Illustration: FIG. 27.--ARCH IN RECEDING PLANES MOULDED.] The first step towards the Gothic system of mouldings was taken by the Romanesque architects when the idea of building arches in thick walls, not only one within the others, but also in planes receding back from the face of the wall one behind as well as within another, was formed and carried out, and when a corresponding recessed arrangement of the jamb of the arch was made (Fig. 26). The next step was the addition of some simple moulding to the advancing angle of each rim of such a series of arches either forming a bead (Fig. 27) or a chamfer. In the transitional part of the twelfth century and the E. E. period this process went on till at last, though the separate receding arches still continued to exist, the mouldings[21] into which they were cut became so numerous and elaborate as to render it often difficult to detect the subordination or division into distinct planes which really remained. [Illustration: FIG. 28.--DOORWAY, KING'S COLLEGE CHAPEL, CAMBRIDGE. (15TH CENTURY.)] This passion for elaborate mouldings, often extraordinarily undercut, reached its climax in the thirteenth century, the E. E. period. In the Dec. period, while almost everything else became more elaborate, mouldings grew more simple, yet hardly less beautiful. In the Perp. period they were not only further simplified, but often impoverished, being usually shallow, formal, and stiff.[22] Ornaments abounded, and included not only enrichments in the shape of carved foliage and figures, statuary, mosaics, and so forth, but ornamental features, such as canopies, pinnacles, arcades, and recesses (Fig. 28).