_Prometheus_ he not only brings Oceanus through the air on a griffin,
but also in a winged chariot introduces the whole choir of ocean nymphs,
at least fifteen in number. There were also hollow places beneath the
stage into which, when necessary, the personages could disappear, and
contrivances for thunder and lightning, for the apparent fall or burning
of a house, &c.

To the hindmost wall of the scene an upper story could be added; whenever,
for instance, it was wished to represent a tower with a wide prospect, or
the like. Behind the great middle entrance there was a space for the
Exostra, a machine of a semicircular form, and covered above, which
represented the objects contained in it as in a house. This was used for
grand strokes of theatrical effect, as we may see from many pieces. On
such occasions the folding-doors of the entrance would naturally be open,
or the curtain which covered it withdrawn.

A stage curtain, which, we clearly see from a description of Ovid, was not
dropped, but drawn upwards, is mentioned both by Greek and Roman writers,
and the Latin appellation, _aulaeum_, is even borrowed from the Greeks. I
suspect, however, that the curtain was not much used at first on the Attic
stage. In the pieces of Aeschylus and Sophocles, the scene is evidently
empty at the opening as well as the conclusion, and seems therefore to
have required no preparation which needed to be shut out from the view of
the spectators. However, in many of the pieces of Euripides, and perhaps
also in the _Oedipus Tyrannus_, the stage is filled from the very first,
and presents a standing group which could not well have been assembled
under the very eyes of the spectators. It must, besides, be remembered,
that it was only the comparatively small proscenium, and not the logeum,
which was covered by the curtain which disappeared through a narrow
opening between two of the boards of the flooring, being wound up on a