ORIGIN OF THE FLYING BUTTRESS
The primitive method of vaulting adopted in the central provinces of
France in the construction of churches with three aisles rendered such
buildings of necessity low and heavy. The main aisle being covered by
a barrel vault, supported on either side by a continuous half-barrel
vault, the sole means of lighting lay in the windows of the side
aisles, so that the nave was always gloomy in the extreme. The
Norman architects had avoided this difficulty, first in their native
province, and afterwards in England, by vaulting the subordinate
aisles only, and by raising the lateral walls of the nave high enough
to allow a line of windows to be introduced between the lean-to roofs
of the side aisles and the nave roof, the latter being an open timber
construction instead of a vault.
The lateral gallery in the first story of Norman churches built on the
basilican model is merely a development of the ancient tradition.[6]
It bears the name of triforium because--or so we are told--each
compartment of such an interior gallery between the main piers of the
nave was originally divided into three by pillars supporting lintels
or by small columns supporting an arcade.
[6] See _L'Architecture Romane_, by Ed. Corroyer; Maison Quantin,
Paris, 1888, chaps. i. iii. and iv.
Towards the close of the eleventh century Norman architects on both
sides of the Channel were raising vast churches, the side aisles of
which bore above their ribbed vaults galleries after the fashion
of the primitive basilicas. These galleries in their turn were
covered by open timber roofs like that of the nave. The bays were
emphasised in the nave and in the side aisles by transverse arches,
or _arcs-doubleaux_, which served as buttresses to those of the main
vault. But after the adoption, towards the middle of the twelfth
century, of the Angevin method of vaulting for religious buildings,
the functions of the lateral walls and of the supporting arches became
better defined, for these walls and arches had now to meet the thrusts
of the transverse as well as that of the diagonal arches, which,
meeting in bundles, as it were, at each pier, gathered their energies
at well-marked points.
It was thus that the cross walls or _arcs-doubleaux_ of the side
aisles were gradually modified till they became detached semi-arches
concealed beneath the outer roof of the side aisles.
We have traced this modification in the Abbaye aux Dames at Caen.[7]
[7] _L'Architecture Romane_, by Ed. Corroyer; Paris, Maison Quantin,
88, chap. xvii.
Fig. 24 shows us an English example. It may be followed out in a
number of other churches in England, at Pavia in Italy, at Zurich in
Switzerland, and at Basle on the Rhine, to name but a few of the
churches in which the modification of the vaults was long posterior to
the construction of the building itself.
[Illustration: 24. DURHAM CATHEDRAL. TRANSVERSE SECTIONS]
In France we shall find no example more deeply interesting than
Noyon, which at the date of its construction (the last quarter of
the twelfth century) formed, as it were, an epitome of the advance
so far made by the architects of the Ile-de-France. In this curious
building we find a fusion of the antique tradition developed by the
Normans in their triforiums, and of the Angevin methods, as manifested
in the groined vaults derived from domes: methods further perfected
by the example of La Ste. Trinité at Angers; in other words, by the
adoption of intersecting arches planned on a square, the thrusts of
all being received on the main piers, reinforced by an intermediate
transverse arch. And we note the appearance of the detached semi-arch
beneath the roofing of the inferior aisles merging at its springing
into the lateral _arc-doubleau_, and so resisting the thrust of the
intersecting arches and transverse arches of the nave.
[Illustration: 25. ABBEY CHURCH AT NOYON. PLAN]
[Illustration: 26. TRANSVERSE SECTION OF NOYON CHURCH]
It has been said that Noyon was suggested by Tournai, doubtless on
account of their superficial affinities. But the likeness is merely in
general aspect, the methods of construction being wholly different. At
Tournai the apsidal transepts are vaulted upon transverse arches of
great strength, and upon radiating semi-arches united where they meet
by a ring of voussoirs set horizontally, and at their springing by
vaults keyed into their mass, an ingenious arrangement which recalls
the vaulting of the _Salle des Capitaines_ over the porch of the
monastery church at Moissac.
The combination of these _arcs-doubleaux_, which, in addition to the
solidity of their independent structure, are strongly reinforced by
the massive circular courses of the walls, is very peculiar, for it
dispenses altogether both with auxiliary arches and with abutments.
Tournai, therefore, cannot be held to have begotten Noyon, for here
we have groined vaults, the intersecting arches of which demand the
reinforcement of abutments either concealed or apparent to sustain
the thrust of these vaults over the lateral _arcs-doubleaux_. The
ingenious arrangement above cited had in no sense modified the methods
of abutment followed by the architects of the twelfth century even
after the adoption of the vault on intersecting arches. These, as will
be remembered, consisted in buttressing the walls and piers of the
nave by cross walls or by arches concealed beneath the roofing of the
side aisles.
[Illustration: 27. CHURCH OF TOURNAI, BELGIUM. EXTERIOR VIEW OF THE
NORTH TRANSEPT TOWARDS THE SCHELDT]
We find at Soissons the first application of an architectural system,
the special feature of which is the _flying buttress_.
[Illustration:28. MONASTERY CHURCH AT MOISSAC. VAULT OF THE HALL KNOWN
AS THE HALL OF THE CAPTAINS ABOVE THE PORCH]
[Illustration: 29. CHURCH OF TOURNAI, BELGIUM. INTERIOR OF THE NORTH
TRANSEPT]
The south transept of Soissons Cathedral was evidently suggested by
Noyon. This is apparent in the adoption of the two-storied side aisle
and in the semi-circular plan. But the method of vaulting common to
both churches has a greater refinement at Soissons. Reduced to its
simplest expression of strength by the attenuation of its skeleton,
the vault still exercises its full thrust on those parts which rise
above the upper gallery.
The architect of Soissons was not content, like his brother of Noyon,
to support the vault laterally by interior arches collaborating with
the _arcs-doubleaux_ of the triforium, and reinforced by an abutment
impinging on the wall of the central nave. To him the idea occurred of
detached semi-arches in open air, springing from above the roof of the
triforium and its buttresses and marking each bay. Thus was born the
_flying buttress_, a feature frankly emphasising its special aim and
function, namely, to meet the thrust of the main vault at its points
of concentration.
[Illustration:30. SOISSONS CATHEDRAL. SOUTH TRANSEPT. SECTION OF
FLYING BUTTRESS]
[Illustration: 31. PERSPECTIVE VIEW OF SOUTH TRANSEPT, SOISSONS
CATHEDRAL[8]]
[8] These flying buttresses, in themselves insufficient for the task
laid upon them, and worn by the destructive action of the weather,
were pushed entirely out of shape by the constant pressure from
within, the thrust of the vault being aggravated by the circular
plan of the building, while the vaults themselves became dislocated
by reason of their insufficient abutments. It became necessary to
reconstruct the buttresses in 1880, to avert the total collapse of the
south transept.
The reconstruction of these flying buttresses, and of many others of
the same period, furnishes us with a criticism _ad hominem_ upon the
system.
The flying buttress, in combination with the intersecting arch,
gave birth to a new system of construction, a system on which
were raised vast buildings which compel our admiration and demand
our careful study, but should not invite our imitation. They are
monuments to the ingenuity of the twelfth and thirteenth century
architect, but no less are they beacons warning against the perils of
a rationalism--more apparent than real--which their authors carried to
its extreme limits, casting to the winds all traditional principles,
and consequently all authority.
It would seem as though the architects of this period, emboldened by
such achievements as the churches of Noyon, Soissons, Laon, Paris,
Sens, and Bourges, and spurred by professional emulation, went on from
one feat of daring to another, passing from the triumphs of Rheims,
Amiens, and Mans to the supreme architectural folly of Beauvais, and
creating monuments no less amazing in dimension than in the statical
problems grappled with, if not always solved.