110

round them and over their top : they are fixed in an in-verted position, and on the side towards the scene aresupported by wedges not less than half a foot high : andopenings are left towards the cavities on the lower bedsof the steps, each two feet long, and a half a foot wide.The following is the rule for determining the situationsof these vases. If the theatre be of moderate size theymust be ranged round at half its height. Thirteencavities are prepared at twelve equal distances from eachother, so that those tones above-named, producing net&hyperbokeon, are to be placed in the cavities at theextreme ends ; second, from the ends, the vessels are tobe of the pitch of netb diezeugmenon, bearing an in-terval of one-fourth from the last mentioned. The thirdnete parameson, an interval of another fourth. Thefourth, nete synemmenon, another fourth. The fifth,mese, a fourth. The sixth, hypate meson, a fourth: inthe centre of the range, hypate hypaton, a fourth. Bythe adoption of this plan, the voice which issues fromthe scene, expanding as from a centre, and strikingagainst the cavity of each vase, will sound with increasedclearness and harmony, from its unison with one orother of them. If, however, the theatre be on a largerscale, the height is to be divided into four parts, so thatthree ranges of cavities may be provided, one for har-monic, the second for chromatic, and the third for dia-tonic vases. That nearest the bottom is for the harmonicgenus as above described, for a lesser theatre. In themiddle range on the extremities, vases producing thechromatic hyperbokeon 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 synemmenon : in the fourth, the chromatic meson,another fourth: in the fifth, the chromatic hypaton, anotherfourth: in the sixth, the paramese, which is a fifth tothe chromatic hyperbokeon, and a fourth to the chro-matic meson. In the centre none are to be placed,