In domestic architecture, if a window were beyond the width of a single casement, a small pillar was often interposed, and the inner order of the window was divided into two arches, while the outer one, if there were any, was in one, the casements or shutters falling into rebates in the back of the column, by which a window of double width, which would not otherwise be conveniently attainable was produced. In window-like openings in which glazing was not needed--as in triforiums, cloisters, and screens--this system was used for beauty where not demanded for the same reasons as in windows, and the subdivisions were often increased to three or four under one comprising arch. [Illustration: Fig. 144.--St. Trophimus, Arles. Cloisters, north side.] In other instances of the same kind, where light arcading was needed, as in cloisters, and the wall was too thick to rest upon a single capital, two small columns were placed one behind another, or a sort of bar or double corbel placed on the capital of a single pillar to support the springer of the arch, for the sake of avoiding the use of thick piers, which were not needed for strength, and would obstruct view and light; and all these practical contrivances were made elements of beauty and varied effect. [Illustration: Fig. 145. Priory Church, Bridlington. Part of remains of Cloisters.] Another legitimate exercise of reason on the part of the Romanesque builders, was the rejection of the fixed rules of proportion observed by the ancients between the diameter and height of their columns. These rules were good in their place, but they had been worked out for a totally different system; and we know that the ancients themselves were anything but as slavish in their adherence to them as their modern imitators. In a purely arcuated system, however, it became clear that such rules were out of place and inconsistent with reason. Circumstances, in a majority of cases, prescribed the height of a column, from reasons wholly irrespective of the question of its load. It followed, then, that the diameter must be regulated rather by the load than the height, so that every variety of proportion became admissible. Take, as an example, the crypt under the choir of York minster. Its height being prescribed by circumstances, and the portion of it required for the vaulting being fixed by the width of the arched bays, it followed that the height of the columns was also rigorously defined; but some of these columns had to carry those of the church above, and with them the whole superstructure, while others had no load but the vaulting of the crypt and the floor of the church. Surely, then, the simplest exercise of reason dictated that their diameters should vary with their load, irrespective of their height. The system of clustering columns both helped to moderate the extremes of such variation in proportion, and, at the same time, introduced still wider liberty; for, though a