From Perinthus to Byzantium it is 630 stadia; from the Hebrus and Cypseli to Byzantium and the Cyanean rocks it is, according to Artemidorus, 3100 stadia. The whole distance from Apollonia on the Ionian Gulf to Byzantium is 7320 stadia; Polybius makes this distance 180 stadia more, by the addition of a third of a stadium to the sum of 8 stadia, which compose a mile. Demetrius of Skepsis, in his account of the disposition of the Trojan forces, says that it is 700 stadia from Perinthus to Byzantium, and the same distance to Parium. He makes the length of the Propontis to be 1400 and the breadth 500 stadia; the narrowest part also of the Hellespont to be 7 stadia, and the length 400. E.