ἐνδεικτικὸν σημεῖον

From LSJ

αἰθὴρ δ᾽ ἐλαφραῖς πτερύγων ῥιπαῖς ὑποσυρίζει (Aeschylus, Prometheus Bound 126) → The bright air fanned | whistles and shrills with rapid beat of wings.

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