HEMICYCLUM was also a part of the orchestra in the ancient theatre. Scaliger, however, observes that it was no standing part of the orchestra, being only used in dramatic pieces, where some persons are supposed to have arrived from sea, as in Plautus's Rudens.
The ancients had also a sort of sun-dial called Hemicyclum. It was a concave semicircle, the upper end or cusp of
which looked to the north. There was a style or gnomon issuing from the middle of the hemicycle, of which that point corresponding to the centre of the hemicycle represented the centre of the earth; and its shadow was projected on the concavity of the hemicycle, which represented the space between one tropic and another, the sun's declination, the day of the month, hour of the day, and so forth.