Change of scene was rarely needed in tragedy; the peculiar arrangements of comedy do not concern us. Only two extant tragedies need it. In the _Eumenides_ of Æschylus the change from the temple of Apollo at Delphi to Athena’s temple in Athens is vital to the plot but need not have caused much trouble; probably convention was satisfied by changing the statue. In _Ajax_ the scene shifts from that hero’s tent to a deserted part of the sea-shore; no doubt the tent was simply removed. One reason against change of scene was the continuous presence of the chorus; when the playwright found he must shift his locality the chorus were compelled to retire and reappear. We read[176] of a permanent appliance by which scenery could be altered; there is, however, no evidence that it was known in the great age of Athenian drama. This consisted of the _periacti_ (περίακτοι). At each end of the scene stood wooden triangular prisms standing on their ends and revolving in sockets, so arranged that one of the narrow oblong sides continued the picture. A different subject was painted on each side. A twist given to either marked a change of place; the alteration of one _periactus_ meant a change of locality within the same region, while the alteration of both meant a complete change of district. Thus, had this contrivance been used in the fifth century, one _periactus_ would have been moved in the _Ajax_, both in the _Eumenides_. Another and stranger use of this contrivance is mentioned by Pollux: “it introduces sea-gods and everything which is too heavy for the machine”. We shall return to this when we come to the “eccyclema” and the “machine”. No curtain is known for the classical age. Stage-properties were few and for the most part simple. Much the most important was the tomb of some great person; that of Darius in the _Persæ_, and of Agamemnon in the _Choephorœ_, are fundamental to the plot, and there are many other examples.[177] Statues have already been mentioned. The spaciousness of the orchestra made it easy to introduce chariots and horses, as in _Agamemnon_, Euripides’ _Electra_ and _Iphigenia at Aulis_.