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their turn are filled with life and moisture。 Now when places become
drier the springs necessarily give out； and when this happens the
rivers first decrease in size and then finally become dry； and when
rivers change and disappear in one part and come into existence
correspondingly in another； the sea must needs be affected。
If the sea was once pushed out by rivers and encroached upon the
land anywhere； it necessarily leaves that place dry when it recedes；
again； if the dry land has encroached on the sea at all by a process
of silting set up by the rivers when at their full； the time must come
when this place will be flooded again。
But the whole vital process of the earth takes place so gradually
and in periods of time which are so immense compared with the length
of our life； that these changes are not observed； and before their
course can be recorded from beginning to end whole nations perish
and are destroyed。 Of such destructions the most utter and sudden
are due to wars； but pestilence or famine cause them too。 Famines；
again； are either sudden and severe or else gradual。 In the latter
case the disappearance of a nation is not noticed because some leave
the country while others remain； and this goes on until the land is
unable to maintain any inhabitants at all。 So a long period of time is
likely to elapse from the first departure to the last； and no one
remembers and the lapse of time destroys all record even before the
last inhabitants have disappeared。 In the same way a nation must be
supposed to lose account of the time when it first settled in a land
that was changing from a marshy and watery state and becoming dry。
Here； too； the change is gradual and lasts a long time and men do
not remember who came first； or when； or what the land was like when
they came。 This has been the case with Egypt。 Here it is obvious
that the land is continually getting drier and that the whole
country is a deposit of the river Nile。 But because the neighbouring
peoples settled in the land gradually as the marshes dried； the
lapse of time has hidden the beginning of the process。 However； all
the mouths of the Nile； with the single exception of that at
Canopus； are obviously artificial and not natural。 And Egypt was
nothing more than what is called Thebes； as Homer； too； shows；
modern though he is in relation to such changes。 For Thebes is the
place that he mentions； which implies that Memphis did not yet
exist； or at any rate was not as important as it is now。 That this
should be so is natural； since the lower land came to be inhabited
later than that which lay higher。 For the parts that lie nearer to the
place where the river is depositing the silt are necessarily marshy
for a longer time since the water always lies most in the newly formed
land。 But in time this land changes its character； and in its turn
enjoys a period of prosperity。 For these places dry up and come to
be in good condition while the places that were formerly well…tempered
some day grow excessively dry and deteriorate。 This happened to the
land of Argos and Mycenae in Greece。 In the time of the Trojan wars
the Argive land was marshy and could only support a small
population； whereas the land of Mycenae was in good condition （and for
this reason Mycenae was the superior）。 But now the opposite is the
case； for the reason we have mentioned： the land of Mycenae has become
completely dry and barren； while the Argive land that was formerly
barren owing to the water has now become fruitful。 Now the same
process that has taken place in this small district must be supposed
to be going on over whole countries and on a large scale。
Men whose outlook is narrow suppose the cause of such events to be
change in the universe； in the sense of a coming to be of the world as
a whole。 Hence they say that the sea being dried up and is growing
less； because this is observed to have happened in more places now
than formerly。 But this is only partially true。 It is true that many
places are now dry； that formerly were covered with water。 But the
opposite is true too： for if they look they will find that there are
many places where the sea has invaded the land。 But we must not
suppose that the cause of this is that the world is in process of
becoming。 For it is absurd to make the universe to be in process
because of small and trifling changes； when the bulk and size of the
earth are surely as nothing in comparison with the whole world。 Rather
we must take the cause of all these changes to be that； just as winter
occurs in the seasons of the year； so in determined periods there
comes a great winter of a great year and with it excess of rain。 But
this excess does not always occur in the same place。 The deluge in the
time of Deucalion； for instance； took place chiefly in the Greek world
and in it especially about ancient Hellas； the country about Dodona
and the Achelous； a river which has often changed its course。 Here the
Selli dwelt and those who were formerly called Graeci and now
Hellenes。 When； therefore； such an excess of rain occurs we must
suppose that it suffices for a long time。 We have seen that some say
that the size of the subterranean cavities is what makes some rivers
perennial and others not； whereas we maintain that the size of the
mountains is the cause； and their density and coldness； for great；
dense； and cold mountains catch and keep and create most water：
whereas if the mountains that overhang the sources of rivers are small
or porous and stony and clayey； these rivers run dry earlier。 We
must recognize the same kind of thing in this case too。 Where such
abundance of rain falls in the great winter it tends to make the
moisture of those places almost everlasting。 But as time goes on
places of the latter type dry up more； while those of the former；
moist type； do so less： until at last the beginning of the same
cycle returns。
Since there is necessarily some change in the whole world； but not
in the way of coming into existence or perishing （for the universe
is permanent）； it must be； as we say； that the same places are not for
ever moist through the presence of sea and rivers； nor for ever dry。
And the facts prove this。 The whole land of the Egyptians； whom we
take to be the most ancient of men； has evidently gradually come
into existence and been produced by the river。 This is clear from an
observation of the country； and the facts about the Red Sea suffice to
prove it too。 One of their kings tried to make a canal to it （for it
would have been of no little advantage to them for the whole region to
have become navigable； Sesostris is said to have been the first of the
ancient kings to try）； but he found that the sea was higher than the
land。 So he first； and Darius afterwards