CIUS(ἡ Κίοςor Κῖος: Eth. Κιανός: Kioor Ghio), a city in Bithynia, at the head of a gulf in the Propontis, called the gulf of Cius, or Cianus Sinus. Herodotus calls it Cius of Mysia; and also Xenophon (Xen. Hell. 1.4.7),—from which it appears that Mysia, even in Xenophon's time, extended at least as far east as the head of the gulf of Cius. According to one tradition, Cius was a Milesian colony. (Plin. Nat. 5.32.) It was at the foot of Mount Arganthonius [ARGANTHONIUS], and there was a myth that Hylas, one of the companions of Hercules on the voyage to Colchis, was carried off by the nymphs, when he went to get water here; and also that Cius, another companion of Hercules, on his return from Colchis, stayed here and founded the city, to which he gave his name. (Strab. p. 564.) Pliny mentions a river Hylas and a river Cius here, one of which reminds us of the name of the youth who was stolen by the nymphs, and the other of the mythical founder. The Cius may be the channel by which the lake Ascania discharges its waters into the gulf of Cius; though Pliny speaks of the Ascanium flumenas flowing into the gulf, and we must assume that he gives this name to the channel which connects the lake and the sea. [ASCANIA.] If the river Cius is not identical with this channel, it must be a small stream near Cius. As Ptolemy (Ptol. 5.1) speaks of the outlets of the Ascanius, it has been conjectured that there may have been two, and that they may be the Hylas and Cius of Pliny; but the plural ἐκβολαίdoes not necessarily mean more than a single mouth; and Pliny certainly says that the Ascanius flows into the gulf. However, his geography is a constant cause of difficulty. The position of Cius made it the port for the inland parts. Mela calls it the most convenient emporium of Phrygia, which was at no great distance from it.
Cius was taken by the Persian general Hymees, after the burning of Sardis, B.C. 499. (Hdt. 5.122.) Philip V., of Macedonia, the son of Demetrius and the father of Perseus, took Cius, which he gave to Prusias, the son of Zelas. Prusias, who had assisted Philip in ruining Cius, restored it under the name of Prusias (Προυσιάς, Strab. p. 563; Plb. 16.21, &c.). It was sometimes called Prusias ἐπιθαλασσίη, or on the sea,to distinguish it from other towns of the same name (Steph. B. s. v. Προῦσα;Memnon, ap. Phot. Cod. 224, 100.43), or θάλασσαν.In the text of Memnon (Hoeschel's ed. of Photius) the reading is Cierus; but Memnon, both in this and other passages, has confounded Cius and Cierus. But it is remarked that Cius must either have still existed by the side of the new city, or must have recovered its old name; for Pliny mentions Cius, and also Mela (1.19), Zosimus (1.35), and writers of a still later date.
There are coins of Cius, with the epigraph Κιανων, belonging to the Roman imperial period; and there are coins of Prusias with the epigraph, Προυσιεων των προς θαλασσαν. [BRYLLIUM.] COIN OF CIUS.
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