I must now return to the discussion of the excellence of the site of Byzantium. The length of the channel connecting the Pontus and Propontis being, as I have said, a hundred and twenty stades, and Hieron marking its termination towards the Pontus, and the Strait of Byzantium that towards the Propontis,—half-way between these, on the European side, stands Hermaeum, on a headland jutting out into the channel, about five stades from the Asiatic coast, just at the narrowest point of the whole channel; where Darius is said to have made his bridge of ships across the strait, when he crossed to invade Scythia. In the rest of the channel the running of the current from the Pontus is much the same, owing to the similarity of the coast formation on either side of it; but when it reaches Hermaeum on the European side, which I said was the narrowest point, the stream flowing from the Pontus, and being thus confined, strikes the European coast with great violence, and then, as though by a rebound from a blow, dashes against the opposite Asiatic coast, and thence again sweeps back and strikes the European shore near some headlands called the Hearths: thence it runs rapidly once more to the spot on the Asiatic side called the Cow, the place on which the myth declares Io to have first stood after swimming the channel. Finally the current runs from the Cow right up to Byzantium, and dividing into two streams on either side of the city, the lesser part of it forms the gulf called the Horn, while the greater part swerves once more across. But it has no longer sufficient way on it to reach the opposite shore on which Calchedon stands: for after its several counter-blows the current, finding at this point a wider channel, slackens; and no longer makes short rebounds at right angles from one shore to the other, but more and more at an obtuse angle, and accordingly, falling short of Calchedon, runs down the middle of the channel.