CHAPTER IV

BUILDINGS VAULTED UPON INTERSECTING ARCHES

The new system derived from the domes upon pendentives, so brilliantly applied in Anjou and Maine in the first half of the twelfth century, was thenceforth the normal method of the religious architect. The admirable simplicity of the new method and its adaptability to every class of building, from the great abbey church to the modest chapel, sufficiently accounts for its rapid dissemination throughout Western Europe, where religious bodies had founded innumerable abbeys, large and small, of varying rules and orders, but all welded together by one mighty organisation.

A long array of churches on the Angevin model rose, not only in the neighbouring provinces--as Ste. Radegonde at Poitiers, Notre Dame de la Coulture and the nave of St. Julien at Mans,--but farther afield towards the south. To name only the most important--the charming Church of Thor, dedicated to Ste. Marie du Lac, between Avignon and the fountain of Vaucluse; that of St. Sauveur at St. Macaire, near Bordeaux; the nave of St. André at Bordeaux, begun in 1252 on the cupola plan, but modified and finally crowned with a groined and ribbed vault; St. Caprais at Agen, which shows the same modifications, and lastly, the immense brick nave of St. Étienne at Toulouse, which measures 64 feet--all demonstrate the progression of the new principles in the second half of the twelfth century.

Towards the North the advance was no less general. Various buildings show to what excellent account contemporary architects had turned the system of vaults on intersecting arches, recognising its admirable adaptability to different climates, and to the most diverse materials. But it was reserved for Angers, the cradle of its birth, to give an added perfection to this ingenious system.

The Church of the Ste. Trinité, on the right bank of the Maine, built by the sons or pupils of those architects who had planned St. Maurice for the hill on the opposite shore, marks a fresh advance in the construction of these vaults. Like St. Maurice, it has but a single aisle, which is divided into three bays, each as nearly as possible square on plan. The system of vaulting takes on a greater elegance by the insertion of a transverse arch, with its supporting shafts, in the centre of each bay. This divides the bay into two equal parts, and, cutting the diagonal ribs at their intersection, supports them at the critical point.

Fig. 19 gives the plan of these vaults, the system of which was eagerly seized upon by the Northern architects, and the great abbey church of Noyon appears to have been the first-fruits of this new development of the Angevin idea.

The great abbey churches and immense cathedrals which were built from the second half of the twelfth to the middle of the thirteenth century attest the importance of the development carried out at Angers by the arrangement of their own vaults in square compartments. For we now find this system adopted in the construction of the churches or cathedrals of Noyon, Laon, Notre Dame at Paris, Sens, and Bourges, to name only acknowledged masterpieces of so-called Gothic.

The influence of the cupola, which we established in our first chapter, was both direct and consecutive. It was direct in churches built with one aisle and vaulted on intersecting arches, and consecutive in the so-called Romanesque churches, which were either completed or modified on the new lines by the substitution of vaults on intersecting arches of dressed stone for timber roofs. A large number of buildings in England, Normandy, Germany, Northern Italy, Switzerland, the Rhine Provinces, and those of Northern France bear testimony of the highest interest to the transformations consequent on the invention of the groined vault and its universal application.

Architects who had been trained in the great abbey schools, emboldened by the successes of their forerunners and their own individual experience, raised on every hand vast cathedrals, in which every known development of the system was essayed with unequalled daring. Going on from strength to strength, they eventually abandoned the antique traditions, and disregarding the statical conditions which ensured the solidity of the ancient buildings, they invented a system of construction which is, as it were, merely a skeleton in stone, a stone version of the timbered roof; its characteristic expression was the permanent strut known as the _flying buttress_; its governing idea was equilibrium, for which it provided by architectural stratagems ingenious in the highest degree, but also extremely precarious. Its existence or stability depends for the most part on the quality of the materials and their degrees of resisting power, the essential organs, by which I mean those vital _weight-carrying_ portions, the failure of which would involve the ruin of the whole, being _outside_ the building, and therefore exposed to all those deteriorating influences from which the _load_ they bear, that is to say, the vaults, are protected by walls and roof.

The great buildings constructed on these new principles consisted of a central nave with two, or even four side aisles. The huge structure depended for its light first upon low windows in the collateral portions, secondly, upon windows at a much higher level. Hence it became necessary to raise the vault of the central nave, and to give it an abutment in the form of _detached semi-arches_ or flying buttresses. The crowns of these semi-arches impinged the piers at the planes of greatest pressure and received the collective thrust of all the ribs, formerets, transverse and diagonal arches. Their bases rested upon abutments, the strength of which was calculated according to the thrust they had to meet.