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round them and over their top: they are fixed in an in-
verted position, and on the side towards the scene are
supported by wedges not less than half a foot high: and
openings are left towards the cavities on the lower beds
of the steps, each two feet long, and a half a foot wide.
The following is the rule for determining the situations
of these vases. If the theatre be of moderate size they
must be ranged round at half its height.
Thirteen
cavities are prepared at twelve equal distances from each
other, so that those tones above-named, producing neté
hyperbolæôn, are to be placed in the cavities at the
extreme ends ; second, from the ends, the vessels are to
be of the pitch of netè diezeugmenön, bearing an in-
terval of one-fourth from the last mentioned. The third
netè paramesôn, an interval of another fourth. The
fourth, netè synemmenôn, another fourth. The fifth,
mesè, a fourth. The sixth, hypatè mesôn, a fourth: in
the centre of the range, hypatè hypatôn, a fourth. By
the adoption of this plan, the voice which issues from
the scene, expanding as from a centre, and striking
against the cavity of each vase, will sound with increased
clearness and harmony, from its unison with one or
other of them. If, however, the theatre be on a larger
scale, the height is to be divided into four parts, so that
three ranges of cavities may be provided, one for har-
monic, the second for chromatic, and the third for dia-
tonic vases. That néarest the bottom is for the harmonic
genus as above described, for a lesser theatre. In the
middle range on the extremities, vases producing the
chromatic hyperbolæon are placed : in the second cavi¬
ties the chromatic diezeugmenon, a fourth from the last:
in the third, at another interval of a fourth, the chro-
matic synèmmenon : in the fourth, the chromatic meson,
another fourth: in the fifth, the chromatic hypaton, another
fourth: in the sixth, the paramesè, which is a fifth to
the chromatic hyperbolæon, and a fourth to the chro-
matic meson. In the centre none are to be placed,
