The sea known as the <a class="linkToPlace" target="_blank" href="/place?placename=Pontus&groupId=910&placeId=1634">Pontus</a> is very nearly twenty-two thousand stades in circumference and has two mouths exactly opposite each other, one communicating the Propontis and the other with the <a class="linkToPlace" target="_blank" href="/place?placename=Palus&groupId=830&placeId=1500">Palus</a> Maeotis, which itself has a circumference of eight thousand stades.
As many large rivers from Asia and still more numerous and larger ones from Europe fall into these two basins, the Maeotis being thus replenished flows into the <a class="linkToPlace" target="_blank" href="/place?placename=Pontus&groupId=910&placeId=1634">Pontus</a> and the <a class="linkToPlace" target="_blank" href="/place?placename=Pontus&groupId=910&placeId=1634">Pontus</a> into the Propontis. The mouth of the <a class="linkToPlace" target="_blank" href="/place?placename=Palus&groupId=830&placeId=1500">Palus</a> Maeotis is called the Cimmerian Bosporus; it is thirty stades in width and sixty in length and is all of no great depth.
The mouth of the <a class="linkToPlace" target="_blank" href="/place?placename=Pontus&groupId=910&placeId=1634">Pontus</a> is similarly called the Thracian Bosporus and is a hundred and twenty stades long and not of the same width throughout.
From the side of the Propontis its beginning is the passage between Calchedon and <a class="linkToPlace" target="_blank" href="/place?placename=Byzantium&groupId=415&placeId=767">Byzantium</a> which is fourteen stades in width.
On the side of the <a class="linkToPlace" target="_blank" href="/place?placename=Pontus&groupId=910&placeId=1634">Pontus</a> it begins at the so‑called Holy Place, where they say that Jason on his voyage back from Colchis first sacrificed to the twelve gods. This lies in Asia and is about twelve stades distant from the opposite point in <a class="linkToPlace" target="_blank" href="/place?placename=Thrace&groupId=1030&placeId=509">Thrace</a> the temple of Sarapis.
There are two causes of the constant flow from the <a class="linkToPlace" target="_blank" href="/place?placename=Palus&groupId=830&placeId=1500">Palus</a> Maeotis and the <a class="linkToPlace" target="_blank" href="/place?placename=Pontus&groupId=910&placeId=1634">Pontus</a>, one, at once evident to all, being that where many streams fall into basins of limited circumference the water constantly increases and, if there were no outlets, would continue to mount higher and occupy a larger area of the basin. In the case, however, of there being outlets the surplus water runs off by these channels. The second cause is that as the rivers carry down into these basins after heavy rains quantities of all kinds of alluvial matter, the water in the seas is forcibly displaced by the banks thus formed and continues to mount and flow out in like manner through the existing outlets.
As the influx and deposit of alluvium by the rivers is constant, the outflow through the mouths must likewise be constant.
The true reasons then of the current flowing from the <a class="linkToPlace" target="_blank" href="/place?placename=Pontus&groupId=910&placeId=1634">Pontus</a> are these, depending as they do not on the reports of traders but on reasoning from the facts of nature, a more accurate method than which it is not easy to find.
Walbank Commentary