e. The fittings of this
part of the building generally include stalls for the clergy and
choristers and a bishop's throne, and are usually beautiful works of
art. Tombs, and inclosures connected with them, called chantry
chapels, are constantly met with in various positions, but most
frequently in the eastern arm.

[Illustration: FIG. 6.--GROUND PLAN OF WESTMINSTER ABBEY.]

Below the raised floor of the choir, and sometimes below other parts
of the building, there often exists a subterranean vaulted structure
known as the crypt.

Passing to the exterior of the cathedral, the principal doorway is in
the western front:[2] usually supplemented by entrances at the ends of
the transepts, and one or more side entrances to the nave. A porch on
the north side of the nave is a common feature. The walls are now seen
to be strengthened by stone piers, called buttresses. Frequently
arches are thrown from these buttresses to the higher walls of the
building. The whole arrangement of pier and arch is called a flying
buttress,[3] and, as will be explained later, is used to steady the
upper part of the building when a stone vault is employed (see Chap.
V.). The lofty gables in which the nave and transepts, and the eastern
arm when square terminate, form prominent features, and are often
occupied by great windows.

In a complete cathedral, the effect of the exterior is largely due to
the towers with which it was adorned. The most massive tower was
ordinarily one which stood, like the central one of Lichfield
Cathedral, at the crossing of the nave and transepts. Two towers were
usually intended at the western front of the building, and sometimes
one, or occasionally two, at the end of each transept. It is rare to
find a cathedral where the whole of these towers have been even begun,
much less completed. In many cases only one, in others three, have
been built. In some instances they have been erected, and have fallen.
In others they have never been carried up at all. During a large
portion of the Gothic period it was usual to add to each tower a
lofty pyramidal roof or spire, and these are still standing in some
instances, though many of them have disappeared. Occasionally a tower
was built quite detached from the church to which it belonged.

To cathedrals and abbey churches a group of monastic buildings was
appended. It will not be necessary to describe these in much detail.
They were grouped round an open square, surrounded by