§ VIII. There are, however, three spaces in which the wall veil, peculiarly limited in shape, was always felt to be fitted for surface decoration of the most elaborate kind; and in these spaces are found the most majestic instances of its treatment, even to late periods. One of these is the spandril space, or the filling between any two arches, commonly of the shape _a_, Fig. LXI.; the half of which, or the flank filling of any arch, is called a spandril. In Chapter XVII., on Filling of Apertures, the reader will find another of these spaces noted, called the tympanum, and commonly of the form _b_, Fig. LXI.: and finally, in Chapter XVIII., he will find the third space described, that between an arch and its protecting gable, approximating generally to the form _c_, Fig. LXI. § IX. The methods of treating these spaces might alone furnish subject for three very interesting essays; but I shall only note the most essential points respecting them. (1.) The Spandril. It was observed in Chapter XII., that this portion of the arch load might frequently be lightened with great advantage by piercing it with a circle, or with a group of circles; and the roof of the Euston Square railroad station was adduced as an example. One of the spandril decorations of Bayeux Cathedral is given in the "Seven Lamps," Plate VII. fig. 4. It is little more than one of these Euston Square spandrils, with its circles foliated. [Illustration: Plate XIV. SPANDRIL DECORATION THE DUCAL PALACE.] Sometimes the circle is entirely pierced; at other times it is merely suggested by a mosaic or light tracery on the wall surface, as in the plate opposite, which is one of the spandrils of the Ducal Palace at Venice. It was evidently intended that all the spandrils of this building should be decorated in this manner, but only two of them seem to have been completed.[82] § X. The other modes of spandril filling may be broadly reduced to four heads. 1. Free figure sculpture, as in the Chapter-house of Salisbury, and very superbly along the west front of Bourges, the best Gothic spandrils I know. 2. Radiated foliage, more or less referred to the centre, or to the bottom of the spandril for its origin; single figures with expanded wings often answering the same purpose. 3. Trefoils; and 4, ordinary wall decoration continued into the spandril space, as in Plate XIII., above, from St. Pietro at Pistoja, and in Westminster Abbey. The Renaissance architects introduced spandril fillings composed of colossal human figures reclining on the sides of the arch, in precarious lassitude; but these cannot come under the head of wall veil decoration.