change in the principles of the construction of the edifice would thus be created. The buttresses now became important members both in the construction and the appearance of the building. The side walls, being now mere enclosing screens, might be reduced from their previous massive condition, and made as thin and light as desired, while the windows in them might be enlarged to any extent. The same remarks apply to the side aisles, the vaulting of which was also groined and supported on buttressed points like the main vaults. With the solid materials of the Romans, the groins or lines of meeting of the intersecting arches formed simple curved lines or angles; but with the smaller materials of the mediæval architects this construction could not easily be accomplished, and it became usual to construct the groins with a solid stone rib, at first plain, but in later examples enriched with a roll moulding. The development of mediæval architecture reached the point above described during the course of the twelfth century. The Romanesque architecture of Lombardy, Germany, and Burgundy had wrought out the arrangement of the groined vaulting and the distribution of the forces arising therefrom, and the designing and construction of the necessary buttresses. The subordination of the various members, the division of the piers and arches into orders, each performing a distinct function, the erection of a vaulting shaft at each pier to receive the ribs of the vaults, the construction of ribs to form the groins and carry the panels of the vaults, had all been fully accomplished. Each shaft was supported on a base and crowned with a cap to receive its load, and each order of the arches received an appropriate moulding or enrichment. Thus far were the constructional features of a genuine arched style of construction, in stone, wrought out during the course of the eleventh and early part of the twelfth centuries. The forms of the ornament kept pace with the development of the construction. In the earlier centuries the Romanesque style had become stereotyped, the general features being regarded as wrought out, and invention limited itself to the elaboration of details and ornaments. Hence it arose that much of the Romanesque ornament was overloaded and inapplicable to its position. But as advances were made in the direction of improving the vaulting and other constructional elements, the builders’ energies were also directed towards improvement of the decorative features, the heavy unsuitable ornaments were discarded, and lighter and more appropriate forms introduced. This new phase of architecture was adopted by the Normans with their usual energy, and during the twelfth century was carried out by them, both in Normandy and England, to an advanced state of development, thus constituting the well-known Norman style. NORMAN STYLE.