86
SPALATO
the building art, and shows us the beginnings of all later forms of consistent arched architecture, Romanesque, Gothic or any other ”; is the parent, therefore, of the long arcades of the great Roman basilicas, such as the original S. Pietro. The architect of Diocletian’s Palace, perhaps first of master-builders, breaks with or abandons the trabeate idea and gives us the free arch. To grasp the meaning of this innovation, so important in the eyes of such competent judges as Freeman, Jackson and Rivoira, we must insist on the difference between a colonnade and an arcade. The colonnade had hitherto preserved the characteristic of its first purpose, use or intention, that is to carry a beam (;trabs); the openings of a colonnade are square-headed; the round-headed opening is characteristic of an arcade. The trabs belonged essentially to wooden construction ; no one dreamed of making, no one could make an arch of a wooden beam. But when stone construction came into use the trabs ceased to he a wooden beam, and became the stone entablature of a colonnade with its component parts of architrave, in which the trabeate name is still preserved, the frieze and the cornice. The definite peculiarity 0 Diocletian’s Palace consists in freeing the arch. abandoning the trabeate idea and turning the ar