Note 136 — PROMETHEUS BOUND
E. H. (Edward Hayes) Plumptre translation
The scene seems at first an exception to the early conventional rule, which forbade the introduction of a third actor on the Greek stage. But it has been noticed that (1) Force does not speak, and (2) Prometheus does not speak till Strength and Force have retired, and that it is therefore probable that the whole work of nailing is done on a lay figure or effigy of some kind, and that one of the two who had before taken part in the dialogue then speaks behind it in the character of Prometheus. So the same actor must have appeared in succession as Okeanos, Io, and Hermes.