How to Study Architecture

by Charles H. Caffin

The mouldings in Hellenic architecture are distinguished by the refinement of the contours, in Roman by the richness of carved ornament.

The anta, which appears in Greek temples at the corners of the cella walls was developed by the Romans into the pilaster. This was a square pier, projecting about one-sixth of its width from the wall; used either to divide up and decorate the wall surfaces, or to serve as a “respond” to a column. It was frequently fluted and corresponded with the column in its details.

Arch-Vaulting.—The Romans did not invent the arch, but generalised its use and elaborated it into vaulting, thus introducing into architecture an element of construction capable of endless application and lending itself not only to utility but also to variety and magnificence. In doing so they were assisted by their discovery of the use of concrete. By means of supports and sheathings of rough timber, temporarily erected, they were able to cast their arches or vaultings in any form and practically of any size. The concrete “set” quickly and the arch or vaulting thus became a solid mass, which exerted but little thrust and covered the space with the rigidity of a lid or cup.

Such method of construction lessened the tendency of the arch or vaulting to exert a lateral strain or thrust which occurs when the arch is composed of voussoirs or, similarly, separate blocks of stone or brick are used in the vault. It tended to concentrate the strain on the vertical supports. Yet the Romans, though concentration of strains was a chief principle of their building, took no chances in the matter of stability and also distributed the strains. For example, the nave vaulting of a basilica would be reinforced by aisle vaulting, which was carried on walls that were either at right angles or parallel to the nave. But owing to the method of concrete construction and to the facility with which it could be employed, the Romans were able to erect vaults over buildings of complex plan and spaces of great size.

The vaultings were of three kinds:

1. The semicylindrical vault, called also the wagon-headed vault or barrel vault.

2. The cross or groined vault.

3. The dome or semidome.

The semicylindrical vault was a continuous arch spanning an oblong space, a corridor, and sometimes a curved passageway.

The cross or groined vault was used over square spaces, its weight being carried at the four angles. It was formed by the intersection at right-angles of two semicylindrical vaults. When employed over long apartments or corridors, the ceiling was divided into a series of square compartments or bays, each covered by a cross-vault. Since the vaulting in each case was carried upon the corner supports, these became piers, and the wall spaces in between them, being thus relieved of the pressure of the vaulting, could be utilised for the openings of doors and windows. Moreover, a square space could be subdivided into bays, rendering it possible to vault a large area with no interruption to the floor-space except that of the piers.