HERE THE REASON IS GIVEN OF THE EFFECTS PRODUCED BY THE WATERS IN
THE ABOVE MENTIONED PLACE.

All the lakes and all the gulfs of the sea and all inland seas are
due to rivers which distribute their waters into them, and from
impediments in their downfall into the Mediterranean --which divides
Africa from Europe and Europe from Asia by means of the Nile and the
Don which pour their waters into it. It is asked what impediment is
great enough to stop the course of the waters which do not reach the
ocean.

On the encroachments of the sea on the land and vice versa
(952-954).