to
which the whole can be subdivided. In France, at any rate during the
earlier periods, the whole series of mouldings would spring from the
square unbroken abacus of a single large column, to which perhaps one
shaft, or as in our illustration (Fig. 36) four shafts, would be
attached which would be carried up to the springing of the nave vault,
at which point the same treatment would be repeated, though on a
smaller scale, with the moulded ribs of that vault.

[Illustration: FIG. 36.--PIERS AND SUPERSTRUCTURE, RHEIMS CATHEDRAL.
(1211-1240.)
_i._ Springing of main ribs of the vault.
_h._ String-course below the clerestory.
_a b._ Triforium arcade.
_g._ String-course below the triform.
B. Main arcade separating the nave from the aisles.
A and N. Shafts attached to pier and supporting portions
of the superstructure.]

A peculiarity of some districts of southern France is the suppression
of the external buttress; the buttresses are in fact built within the
church walls instead of outside, and masonry enough is added to make
each into a separating wall which divides side chapels. Some large
churches, _e.g._, the cathedral at Alby, in Southern France, consist
of a wide nave buttressed in this way, and having side chapels between
the buttresses, but without side aisles.

The plans of the secular, military, and domestic buildings of France
also present many interesting peculiarities, but not such as it is
possible to review within the narrow limits of this chapter.

_Roofs and Vaults._

The peculiarly English feature of an open roof is hardly ever met with
in any shape: yet though stone vaults are almost universal, they are
rarely equal in scientific skill to the best of those in our own
country. In transitional examples, many very singular instances of the
expedients employed before the pointed vault was fully developed can
be found. In some of the central and southern districts, domes, or at
least domical vaults, were employed. (See the section of Fontevrault,
Fig. 31). The dome came in from Byzantium. It was introduced in
Perigord, where the very curious and remarkable church of St. Front
(begun early in the eleventh century) was built. This is to all
intents a Byzantine church. It is an almost exact copy in plan and
construction of St. Mark's at Venice, a church designed and built by
Eastern architects, and it is roofed by a series of