of the simple and symbolical character which marked Greek stage scenery in general; a rock would stand for a mountainous district, a waved blue line and a dolphin for the sea, a river god perhaps, holding a vessel of water, for a river.[609] Besides their use in effecting a change of scene, the periaktoi were also employed to introduce sea-gods and objects too heavy for the mechane. It is not said how this was managed. But it is possible that, of the two sides of the periaktos which were out of sight of the audience, one contained a small ledge or balcony, on which the sea-god took his stand. As the machine rolled round, he would come suddenly into view.[610] It is difficult to say when the periaktoi were first introduced, and whether they were used at all during the classical period of the Greek drama. They are mentioned by one grammarian among a list of stage appliances which might be ascribed to Aeschylus,[611] and it is true that they might have been used in producing the change of scene in the Eumenides from the temple at Delphi to the temple at Athens. But they could have been easily dispensed with. In fact, as far as the extant Greek dramas are concerned, there are no occasions on which it is necessary to suppose that they were used, and there are no passages in which they are referred to.[612] The periaktoi, as stated above, are the only appliances for changing scenery that are mentioned in Greek writings. Servius describes another kind of contrivance, by means of which the scene was parted asunder in the middle, and then drawn aside in both directions, so as to disclose a new scene behind.[613] But it is probable that this invention dated from comparatively late times. There is nothing in the existing Greek dramas to suggest that such a contrivance was in use during the classical period. § 5. _Stage Properties, &c._