Norman clerestory; but above them, stretching all along each side of the nave, may be seen the windows of the present clerestory. These are Perpendicular in style, and are five in number on each side, each window being placed over one of the piers of the nave arcading. These windows are square-headed, and have at the bottom three lights, each light being sub-divided into two at the top. It is believed that this clerestory was formed when the walls were raised, at the same time as the western tower was erected--namely, at the end of the fifteenth century. But to return to the Decorated arches at the west end of the nave. The pier at the eastern side of the easternmost of these consists of the semi-cylindrical respond of Norman date, a piece of masonry which was part of the west wall of the Norman church; and then on the western side of this an added semi-cylinder, on the capitals of which may be seen the ball-flower ornament. The pier on either side, between the two fourteenth-century arches, is octagonal, with a very plain capital (one of these is shown in the illustration on page 57); the arches themselves are also plain, consisting of two members with chamfered edges. The half pillars at the western side of the western arch have been imbedded in the octagonal buttresses of the west tower, which project into the church. [Illustration: PIER AND ARCH-SPRING IN THE SOUTH ARCADE.] [Illustration: DECORATED ARCH IN THE NAVE.] The height of the nave roof appears to have been altered on several occasions. There may be seen from the interior of the nave, on the west wall of the lantern tower, two lines running from the level of the tops of the Norman clerestory windows: these make an angle of about forty-five degrees with the horizontal, and, no doubt, are traces of the weather mouldings marking the position of the exterior of the roof of the nave in Norman times. Probably the roof visible from the interior was flat and formed of wood, and ran across in the line of the string course above the tower arch, at a level slightly above the heads of the clerestory windows. A round-headed opening above this string course probably gave admission to the space between the outer and inner roofs. At a somewhat higher level, we have a slight trace which probably marks the junction of the fifteenth-century roof with the tower. This roof was of oak and very plain--at the restoration the pitch of the roof was raised and carried up to such an extent as to cut off the bases of the clerestory windows of the lantern tower; the inner roof itself is of pitch-pine, with hammer-beams of the character which finds such favour with nineteenth-century architects. [Illustration: CLERESTORY STAGE OF THE CENTRAL TOWER.]