Polybius, Histories

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The Black Sea

The sea called "The Pontus" has a circumference of

The Pontus.

twenty-two thousand stades, and two mouths diametrically opposite to each other, the one opening into the Propontis and the other into the Maeotic Lake; which latter also has itself a circumference of eight thousand stades. Into these two basins many great rivers discharge themselves on the Asiatic side, and still larger and more numerous on the European; and so the Maeotic lake, as it gets filled up, flows into the Pontus, and the Pontus into the Propontis. The mouth of the Maeotic lake is called the Cimmerian Bosporus, about thirty stades broad and sixty long, and shallow all over; that of the Pontus is called the Thracian Bosporus, and is a hundred and twenty stades long, and of a varying breadth. Between Calchedon and Byzantium the channel is fourteen stades broad, and this is the entrance at the end nearest the Propontis. Coming from the Pontus, it begins at a place called Hieron, at which they say that Jason on his return voyage from Colchis first sacrificed to the twelve gods. This place is on the Asiatic side, and its distance from the European coast is twelve stades, measuring to Sarapieium, which lies exactly opposite in Thrace. There are two causes which account for the fact that the waters, both of the Maeotic lake and the Pontus, continually flow outwards. One is patent at once to every observer, namely, that by the continual discharge of many streams into basins which are of definite circumference and content, the water necessarily is continually increasing in bulk, and, had there been no outlet, would inevitably have encroached more and more, and occupied an ever enlarging area in the depression: but as outlets do exist, the surplus water is carried off by a natural process, and runs perpetually through the channels that are there to receive it. The second cause is the alluvial soil brought down, in immense quantities of every description, by the rivers swollen from heavy rains, which forms shelving banks and continually forces the water to take a higher level, which is thus also carried through these outlets. Now as this process of alluvial deposit and influx of water is unceasing and continuous, so also the discharge through the channels is necessarily unceasing and continuous.

These are the true causes of the outflow of the Pontus, which do not depend for their credit on the stories of merchants, but upon the actual observation of nature, which is the most accurate method discoverable.