By the time that the Hellenic theatre had evolved into a permanent structure, the _skene_, originally a temporary screen, took the form of an architectural background, some ten feet high, with a central door for the entrances of the actors. But the idea of the original screen was perhaps retained in the row of columns which stood a little in front of the _skene_, and could be used, if needed, for the hanging of curtains or even of painted cloths. Meanwhile, the roof of the portico, which extended from the columns to the _skene_, could be utilised by the actors at certain stages of the drama.[5] The interest of the discussion raised by Vitruvius’ description consists in the question how far the actors mingled with or were separated from the chorus, which continued to occupy the _orchestra_ or circle on the floor of the auditorium, corresponding to the place of the orchestra stalls in a modern theatre. The orchestra of a Greek theatre was originally the sole “stage,” but gradually, as the dramas involved more complexity of scenes, the actors would vary their position between the orchestra and the proscenium; and later, in Hellenistic times, as the religious origin of the drama was forgotten and the use of a chorus began to fall into abeyance, the use of the proscenium would increase. Finally, when the Romans began to imitate the Greek drama, they dropped the chorus; the acting was confined to the proscenium, and the orchestra no longer needed for the play, became a part of the auditorium, reserved for distinguished spectators. The Roman theatre, in fact, like our own, represented the complete separation of the audience and the stage. =Odeion.=--Supplementing the theatre was the Odeion or concert hall, which was constructed on the same general lines but distinguished by the addition of a roof for acoustic purposes. The oldest known is the =Skias= at Sparta, so called from its roof resembling the top of a parasol. The =Odeion of Pericles=, which served as a model for subsequent halls, was built on the southeastern slope of the Acropolis, its roof being made in imitation of the tent of Xerxes and constructed of the masts of Persian vessels, captured at the battle of Salamis. The most magnificent example, however, was erected <small>A.D.</small> 162 on the southwest slope, by a wealthy citizen, =Herodes Atticus=, in memory of his wife. Its ceiling is said to have been composed of beams of cedar, carved with ornament, while decorations in the form of paintings and other works of art embellished the interior, which had accommodation for eight thousand persons. CHAPTER III ROMAN CIVILISATION