has hardly been realised how many of the greater "Norman" churches in England were vaulted, especially their eastern limbs and transepts. The eastern limb of the great abbey church of St Albans, begun about ten years after the Conquest, was vaulted. Durham and Lincoln cathedrals were vaulted throughout, by the middle of the twelfth century. The abbey churches of Gloucester, Pershore and Tewkesbury all seem to have had vaulted choirs and transepts; so probably had Canterbury cathedral, Winchester cathedral, St Paul's cathedral, Reading abbey and Lewes priory churches and many others. Frequently the nave was covered with a wooden ceiling while the eastern half of the church was vaulted. At Peterborough such a ceiling, delightfully decorated with bold pattern-work, still exists. This church and others had such ceilings throughout. The "glorious choir" at Canterbury had a specially famous painted ceiling. It is noteworthy that even in quite small churches the chancels were frequently covered with vaults, while the rest of the structure had wooden roofs.
Many modifications were made in the planning of great churches to accommodate the vaults, and a remarkable contrivance became common towards the end of the twelfth century for the purpose of supporting the high central vaults. This was the flying buttress, a strong arch built in the open air, rising from the lower walls of the aisles, and butting against those of the clerestory. Such buttresses were greatly developed in Gothic architecture, but their invention is due to Romanesque builders. Another great invention, which was of primary importance for the development of Gothic, seems to have been made towards the end of the eleventh century. This was the method of erecting vaults by first building a series of skeleton arches (ribs) diagonally across each bay, and then covering this subdivided space with a lighter web of work. In England the method was used at Durham, and this is the first well-authenticated instance in the west of Europe. Other examples, which are said to be earlier, are known in Italy.
The general movement, which was to pass over an invisible frontier into what we call Gothic architecture, was characterised by a search for more vigorous and clear solutions of structural problems, a gathering up of the wall masses into piers and buttresses and the vaults into ribs. The whole medieval process in architecture from, say, the time of Charlemagne to the time of the Black Death, was an organic development. One phase in the progress may be traced in the tendency to break up piers and arches into a series of recessed orders or members; that is, they widen by degrees in a step-like profile. This held the germ of the change from a square pier set in the direction of the wall into one placed diagonally. Such membering of arches and piers easily led to sub-arching, that is, the including of two or more smaller arches under a larger one; and this again was to lead up to the development of tracery. The process also early shewed itself in a liking for alternation.
