The space between the two parodi and leading past the scene-building was usually thought of as representing a street or roadway (see p. 86, above). In the Hellenistic theater at Athens a stone proscenium ran across the front of the scene-building from one parascenium to the other (see p. 70, above) (Fig. 38), and it is likely that a wooden proscenium occupied the same space from about 430 B.C. It is true that the stone foundation of the parascenia, which were probably erected to serve as a framework for the proscenium, cannot go back of 415-421 B.C. at the earliest (see p. 67 and n. 1, above). But it is fair to assume that parascenia entirely of wood were erected as an experiment a few years before permanent foundations were provided for them, and the proscenium colonnade seems to have been employed at least as early as Euripides’ _Hippolytus_ (428 B.C.) and Aristophanes’ _Clouds_ (423 B.C.). Confirmation for this conclusion may be found in the fact that the crane (μηχανή) was introduced at about this same time (see p. 289, below). When the scene was laid before a private house or a palace, the colonnade was in place as signifying its prothyron (πρόθυρον) or “porch.” When the background was thought of as a temple the proscenium was its _pronaos_ (πρόναος) or “portico.” Moreover, when a less conventional setting was required, painted panels (πίνακες) could be inserted in the intercolumniations in order to suggest the desired locality, and in some theaters the proscenium columns were shaped so as to hold such panels more firmly in place (Fig. 72).[312] Thus the action in Sophocles’ _Oedipus at Colonus_ takes place before a grove, and that in Plautus’ _The Fisherman’s Rope_, along a beach. The interruption of natural scenery by columns at regular intervals would be disturbing to us; that it did not seem so to the Greeks was due not only to their ignorance of modern scenery but also to the sketchy shorthand which they practiced in other fields of art. On ancient vases, for example, a whole forest is frequently represented by a single tree. A similar convention obtains in the drama of modern Persia, where “the desert is represented by a handful of sand on the platform, the river Tigris by a leather basin full of water.”[313] Sophocles is said to have invented scene painting during the lifetime of Aeschylus (see p. 66, above), but this must be interpreted as meaning that he had the panels applied directly to the front of the scene-building, the proscenium being not yet introduced. It has also been suggested, on the basis of certain vase paintings (Fig. 73),[314] that an actual porch (prothyron) was sometimes built extending from the center of the proscenium or taking the place of a proscenium and extending from the center of the scene-building’s front wall. But perhaps these paintings are only conventionalized representations of the proscenium colonnade itself. In any case it is important to observe that no background