g to which it is an appendage.

TYMPANUM.--The filling in of the head of an arch, or
occasionally of an ornamental gable.

UNDERCUTTING.--A moulding or ornament of which the greater
part stands out from the mouldings or surfaces which it
adjoins, as though almost or quite detached from them, is
said to be undercut.

VAULT.--An arched ceiling to a building, or part of a
building, executed in masonry or in some substitute for
masonry.

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