I must now resume my account of the specially favourable situation of <a class="linkToPlace" target="_blank" href="/place?placename=Byzantium&groupId=415&placeId=767">Byzantium</a>. The channel connecting the <a class="linkToPlace" target="_blank" href="/place?placename=Pontus&groupId=910&placeId=1634">Pontus</a> and the Propontis being a hundred and twenty stades in length, as I just said, the Holy Place marking its termination towards the <a class="linkToPlace" target="_blank" href="/place?placename=Pontus&groupId=910&placeId=1634">Pontus</a> and the strait of <a class="linkToPlace" target="_blank" href="/place?placename=Byzantium&groupId=415&placeId=767">Byzantium</a> that towards the Propontis,
halfway between these on the European side stands the Hermaeum on a promontory running out into the channel at a distance of about five stades from Asia and situated at the narrowest part of the whole. It is here, they say, that Darius bridged the straits when he crossed to attack the Scythians.
Now the force of the current from the <a class="linkToPlace" target="_blank" href="/place?placename=Pontus&groupId=910&placeId=1634">Pontus</a> has been so far uniform owing to the similarity of the country on each bank of the channel,
but when it reaches the Hermaeum on the European side, which is, as I said, the narrowest point, this current from the <a class="linkToPlace" target="_blank" href="/place?placename=Pontus&groupId=910&placeId=1634">Pontus</a> being confined and sweeping strongly against the headland, rebounds as if from a blow, and dashes against the opposite coast of Asia.
It now again recoils from this coast and is carried against the promontory on the European bank known as the Hearths,
from which its force is once more deflected to the place on the Asiatic bank called the Cow, where legend says that Io first found a footing after crossing.
Finally the current runs rapidly from the Cow to <a class="linkToPlace" target="_blank" href="/place?placename=Byzantium&groupId=415&placeId=767">Byzantium</a> itself, and dividing into two near the city, sends off its smaller branch into the gulf known as the Horn, while the larger branch is again deflected.
It has however, no longer sufficient force to reach the coast opposite, on which stands Calchedon;
for as it has now several times crossed and recrossed the channel, which here is already of considerable width, the current has now become feebler, and ceases to make short rebounds to the opposite coast at an acute angle, but is rather deflected at an obtuse angle.
It therefore fails to reach Calchedon and flows out through the strait.
Walbank Commentary