OF THE ORIGIN OF RIVERS.

The body of the earth, like the bodies of animals, is intersected
with ramifications of waters which are all in connection and are
constituted to give nutriment and life to the earth and to its
creatures. These come from the depth of the sea and, after many
revolutions, have to return to it by the rivers created by the
bursting of these springs; and if you chose to say that the rains of
the winter or the melting of the snows in summer were the cause of
the birth of rivers, I could mention the rivers which originate in
the torrid countries of Africa, where it never rains--and still less
snows--because the intense heat always melts into air all the clouds
which are borne thither by the winds. And if you chose to say that
such rivers, as increase in July and August, come from the snows
which melt in May and June from the sun's approach to the snows on
the mountains of Scythia [Footnote 9: Scythia means here, as in
Ancient Geography, the whole of the Northern part of Asia as far as
India.], and that such meltings come down into certain valleys and
form lakes, into which they enter by springs and subterranean caves
to issue forth again at the sources of the Nile, this is false;
because Scythia is lower than the sources of the Nile, and, besides,
Scythia is only 400 miles from the Black sea and the sources of the
Nile are 3000 miles distant from the sea of Egypt into which its
waters flow.

The tide in estuaries.