With reference to the division of interiors into parts, the same two types are exemplified which we found in studying the visual and the dynamic aspects of buildings. Either the parts of the interior space are clearly marked off from each other, and the perception of the whole which they constitute is reached by a process of summation; or else, to one standing within, the space is first perceived as a whole, and its parts, lacking clear definition, are perceived subsequently. In the former type, the parts are of pronounced individuality, and the whole is their free and joint work; in the latter, the parts are merged, and tend to be lost in the whole. These two possibilities exist whether the space be of radial or longitudinal form. In general, the classical styles lend themselves to the coordinate type of division of the interior, while the later styles favor the subordination of the parts to the whole. The other factors in the beauty of architecture, besides the expression of the forces resident in its forms, can receive only scant notice from us. Among these is light--its admission, exclusion, and diffusion. A house with ample windows flooded with sunshine shares the feeling of an open day; a cathedral, dimly lighted, stimulates a mood of brooding mystery and meditation, like some dark forest. Another factor is color. Color plays a double part in architecture: first, to enliven the neutral tones of certain materials; and second, to impart specific moods. It was no barbaric taste, but a keen feeling for life and warmth that induced the Greeks to paint their temples; and without their rose windows, Gothic cathedrals are like faces from which the glow of life is departing. The different colors have the same feelings in architecture that they have in painting. The reds and purples of ecclesiastical stained glass stimulate the passion of adoration, the blues deepen it, and the yellows seem to offer a glimpse of heavenly bliss. Sound, its presence or its absence, is another factor in architectural expression: the quiet of the church in contrast with the noise of the busy street outside, the peal of the organ, or the chorus of young voices. Although architecture is a spatial art and music a temporal art, they nevertheless go well together because the emotions aroused by both are vague and voluminous, and the sounds, reverberating from the walls and filling the inclosed spaces, seem to fuse with them. Ornamental carving performs a diversifying and enlivening function similar to that of color. So long as its lines follow those of the architectural forms, it may well be rich and elaborate. It is fitting, moreover, that buildings designed to be houses of the gods should contain their images, and that the same spirit that expresses itself in playful lines should become embodied in griffin and gargoyle. Finally, erected in the open, with no shelter or enframement, a building is, in large measure, a part of nature and possesses something of the