The important feature of the river is its annual inundation. At the end
of May the river is at its lowest level, it rises gradually in June and
continues rising until the middle of September; it then remains
stationary from two to three weeks, rising again until the end of
October; it is then at its highest level and begins gradually to fall,
until by May it is once more at its lowest. The river rises from
twenty-one to twenty-eight feet; when it did not reach this level the
crops failed, and when it exceeded it, the land was overflowed and ruin
faced the people. Nowhere in the world is there such a large population
depending solely on the produce of the soil.