The vaults of the Norman period were simple barrel- or waggon-headed vaults, and semicircular arches only were used in their construction. With the Gothic period the use of intersecting, and as a result of pointed arches, was introduced into vaulting, and vaults went on increasing in complexity and elaboration till the Tudor period, when fan-vaulting was employed. Our illustrations show some of the steps in the development of Gothic vaults referred to in Chapter V. of the text. No. 1 represents a waggon-head vault with an intersecting vault occupying part of its length. No. 2 represents one of the expedients adopted for vaulting an oblong compartment before the pointed arch was introduced. The narrower arch is stilted and the line of the groin is not true. No. 3 represents a similar compartment vaulted without any distortion or irregularity by the help of the pointed arch. No. 4 represents one lay of a sexpartite Gothic vault. No. 5 represents a vault with lierne ribs making a star-shaped pallom on plan, and No. 6 is a somewhat more intricate example of the same class of vault. [Illustration: FIG. _G G_.--VAULTS.] Vaults are met with in Renaissance buildings, but they are a less distinctive feature of such buildings than they were in the Gothic period; and in many cases where a vault or a series of vaults would have been employed by a Gothic architect, a Renaissance architect has preferred to make use of a dome or a series of domes. This is called domical vaulting. Examples of it occur occasionally in Gothic work. WAGGON-HEAD VAULTING, OR BARREL-VAULTING.--A simple form of tunnel-like vaulting, which gets its name from its resemblance to the tilt often seen over large waggons, or to the half of a barrel. WAINSCOT.--(1) The panelling often employed to line the walls of a room or building; (2) a finely marked variety of oak imported chiefly from Holland; probably so called because wainscot oak was at one time largely employed for such panelling. WEATHERING.--A sloping surface of stone employed to cover the set-off (which see) of a wall or buttress and protect it from the effects of weather. WHEEL WINDOW.--A circular window, and usually one in which mullions radiate from a centre towards the circumference like the spokes of a wheel; sometimes called a rose-window. WINDOW-HEAD.--For illustrations of the various forms and filling-in of Gothic window-heads, see the words Arch and Tracery. [Illustration: {ORNAMENTAL DOLPHIN PATTERN.}] HEAD AND TAILPIECES. PAGE HEADPIECE.--CRÊTE FROM NOTRE DAME, PARIS 1 " SCULPTURED ORNAMENT FROM RHEIMS CATHEDRAL 6 " " " SENS CATHEDRAL 21