in the main design, and sometimes capriciously renewing itself throughout, as in the cylindrical niches and pedestals which enrich the porches of Caudebec and Rouen. Fig. 1, Plate I. is the simplest of those of Rouen; in the more elaborate there are four projecting sides, divided by buttresses into eight rounded compartments of tracery; even the whole bulk of the outer pier is treated with the same feeling; and though composed partly of concave recesses, partly of square shafts, partly of statues and tabernacle work, arranges itself as a whole into one richly rounded tower. [Illustration: PLATE V.--(Page 88--Vol. V.) CAPITAL FROM THE LOWER ARCADE OF THE DOGE'S PALACE, VENICE.] XVII. I cannot here enter into the curious questions connected with the management of larger curved surfaces; into the causes of the difference in proportion necessary to be observed between round and square towers; nor into the reasons why a column or ball may be richly ornamented, while surface decorations would be inexpedient on masses like the Castle of St. Angelo, the tomb of Cecilia Metella, or the dome of St. Peter's. But what has been above said of the desireableness of serenity in plane surfaces, applies still more forcibly to those which are curved; and it is to be remembered that we are, at present, considering how this serenity and power may be carried into minor divisions, not how the ornamental character of the lower form may, upon occasion, be permitted to fret the calmness of the higher. Nor, though the instances we have examined are of globular or cylindrical masses chiefly, is it to be thought that breadth can only be secured by such alone: many of the noblest forms are of subdued curvature, sometimes hardly visible; but curvature of some degree there must be, in order to secure any measure of grandeur in a small mass of light. One of the most marked distinctions between one artist and another, in the point of skill, will be found in their relative delicacy of perception of rounded surface; the full power of expressing the perspective, foreshortening and various undulation of such surface is, perhaps, the last and most difficult attainment of the hand and eye. For instance: there is, perhaps, no tree which has baffled the landscape painter more than the common black spruce fir. It is rare that we see any representation of it other than caricature. It is conceived as if it grew in one plane, or as a section of a tree, with a set of boughs symmetrically dependent on opposite sides. It is thought formal, unmanageable, and ugly. It would be so, if it grew as it is drawn. But the power of the tree is not in that chandelier-like section. It is in the dark, flat, solid tables of leafage, which it holds out on its strong arms, curved slightly over them like shields, and spreading towards the extremity like a hand. It is vain to endeavor to paint the sharp, grassy, intricate leafage, until