dividing walls should act as stays to their vaults, [1] or else they resorted to the methods before noticed of employing such vast thickness of wall as to secure stability by sheer inertia of material.
FIG. 4.
The Romanesque builders went a step farther in the development of the buttress, in accordance with their general progress in the art of construction. They at first placed a pilaster strip on the outside of the wall against the pressure that was to be met, treating it as a distinct functional member (Fig. 5). It is true that the 
FIG. 5. Romans had employed engaged columns in the same positions, but they had employed them for a decorative purpose only. And even in early Romanesque constructions the pilaster strip had little more than a decorative value. It did, indeed, stiffen the wall somewhat, this was the reason for its use, the walls of Romanesque buildings not having the great thickness that was common in Roman walls, but it had not projection enough to bear much vault pressure. It had, however, rarely to meet such pressure, except in the aisles
- ↑ See August Choisy, L'Art de Batir chez les Romains, p. 93, et seq.
