420 COMPAKATIVl-: ARCHITECTUKK. The widely-spaced nave arcades are characteristic, the triforium being usually omitted, as at Florence and Milan (No, 176), and the clerestory reduced to the unimportance of a vault spandrel, pierced by a small, and generally circular, window. These lofty arcades practically include the aisles and nave in one composition and give the effect of a single hall. The nave vaulting is frequently set out in square compart- ments, as at Florence Cathedral (No. 176 d) and the Certosa, Pavia, the side aisles having oblong ones, thus reversing the Northern Gothic practice. Towers, usually isolated, have square shafts without buttresses, sometimes beautifully decorated, continuing the Romanesque tra- dition, and developing no spire growth, like northern examples. The best known are at Florence (No. 181), Siena (No. 182), Lucca, Verona (No. 184 k), Mantua and Pistoja. The most imposing external feature was frequently a dome, as at Siena (No. 182) and Florence (No. 181). The central lantern tower, in diminishing stages, as at Chiara- valle, the Certosa at Pavia, and Milan Cathedral (No. 176), are an advance on the Romanesque lanterns at the crossing, and may be compared with English work. B. Walls. — The absence of large windows obviated the necessity for projecting buttresses, the high and flat walls being usually comparatively solid throughout their length, and able themselves to withstand the pressure of a vault (Nos. iSi and 182). From the absence of vertical features and shadows in the fa9ade, flatness is the predominant characteristic of the style. Fa9ades are treated independently as decorative compositions, and often have no relation to the structure or roofs behind (No. 182). These fa9ades are often incomplete, being composi- tions in marble facing, in many cases not finished on the score of expense. The marble was used in bands of two colors at Siena (No. 182) and Orvieto, each having three high gables, and in panelling at Florence (No. 181). This surface treat- ment was borrowed from the Saracens, and may be compared with northern methods, in which effect is obtained by deeply- moulded string courses, projecting buttresses, and lofty pinnacles. c. Openings. — The windows are often semicircular headed, and have shafts with square capitals of Corinthian type, instead of the moulded mullions of northern Gothic examples (No. 184 c). These slender shafts are often twisted, and even inlaid with glass mosaic known as " cosmato " work, from the family of that name, while the capitals are richly sculptured. Venetian tracery is a special form of geometrical combinations (No. 178). A moulded keystone is often provided to pointed arches, which are frequently inclosed by square lines as a frame.
