The _Pillars_ are usually round or octagonal. They are built of large blocks of dressed stone, and so differ from the Norman pillars, which consisted of rubble with a facing of stone. In the more important buildings they are formed of four or more slender shafts of Purbeck marble, which are placed around a large circular column of stone, and their dark colour causes them to “stand out” against the paler central stone pier. The _Arches_ vary in form from a very blunt to a very sharp point, but they are generally acutely pointed, and are often richly moulded, as in Westminster Abbey. The mouldings, however, are the safest guide to the style, as the form of the pointed arch largely depends on convenience. As a rule, they are generally more acutely pointed in the cathedrals and large churches, whilst they are broader in small churches. The _Windows_ in earlier examples are plain, long, and narrow, with acutely pointed heads. They are frequently spoken of as “lancet-shaped.” The earliest form is that of a single light, with arched head and without moulding of any kind, external or internal. (Pl. 34, Fig. 1.) Windows of four lights are occasionally met with, but generally they consist of three, five, or seven lights, rising in height to the central one. They are often included under an arched moulding called a “dripstone.” (Pl. 34, Figs. 2, 3, 4A.) Square-headed windows are not uncommon, but sometimes in these cases there is an arch or a dripstone in the form of an arch over the window. When two lights were combined under one arch, a blank space called a “tympanum” was left between the heads of the lights and the arch; but in time this space began to be pierced with another small light, generally in the form of a circle, a trefoil, or a quatrefoil, which both relieved the blank space and admitted more light. (Pl. 34, Fig. 3.) When this is done in the stone work, it is called _plate tracery_, and from this is developed the window tracery of later times. The Normans were doubtful about their skill in making ceilings of stone to cover large spaces, and consequently they generally built timber roofs. Over small spaces, however, they erected stone ceilings or “vaults,” which were quite plain. In this period the vaults are distinguished by having ribs in the angles of the groins, with carved masses of foliage in stone, called bosses, at the intersection of the ribs. (Pl. 34, Fig. 5.) The _Buttresses_ (Pl. 35, Figs. 4, 5, and 6), instead of being merely flat strips of masonry, slightly projecting from the wall, as in the Norman Period, have now a bold projection, generally diminished upwards by stages, and terminate in a plain slope or a gable. By the use of this form of buttress it was possible to reduce the thickness of the wall. The corner of the building had a pair of buttresses at right angles to the wall, as if each wall had been continued beyond the point of junction--never one buttress placed diagonally, as in subsequent periods.