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evaporation has not had time to develop or that it has passed away and
there is none as yet to replace it。
Both the setting and the rising of Orion are considered to be
treacherous and stormy； because they place at a change of season
（namely of summer or winter； and because the size of the constellation
makes its rise last over many days） and a state of change is always
indefinite and therefore liable to disturbance。
The Etesiae blow after the summer solstice and the rising of the
dog…star： not at the time when the sun is closest nor when it is
distant； and they blow by day and cease at night。 The reason is that
when the sun is near it dries up the earth before evaporation has
taken place； but when it has receded a little its heat and the
evaporation are present in the right proportion； so the ice melts
and the earth； dried by its own heat and that of the sun； smokes and
vapours。 They abate at night because the cold pf the nights checks the
melting of the ice。 What is frozen gives off no evaporation； nor
does that which contains no dryness at all： it is only where something
dry contains moisture that it gives off evaporation under the
influence of heat。
The question is sometimes asked： why do the north winds which we
call the Etesiae blow continuously after the summer solstice； when
there are no corresponding south winds after the winter solstice？
The facts are reasonable enough： for the so…called 'white south winds'
do blow at the corresponding season； though they are not equally
continuous and so escape observation and give rise to this inquiry。
The reason for this is that the north wind I from the arctic regions
which are full of water and snow。 The sun thaws them and so the
Etesiae blow： after rather than at the summer solstice。 （For the
greatest heat is developed not when the sun is nearest to the north；
but when its heat has been felt for a considerable period and it has
not yet receded far。 The 'bird winds' blow in the same way after the
winter solstice。 They； too； are weak Etesiae； but they blow less and
later than the Etesiae。 They begin to blow only on the seventieth
day because the sun is distant and therefore weaker。 They do not
blow so continuously because only things on the surface of the earth
and offering little resistance evaporate then； the thoroughly frozen
parts requiring greater heat to melt them。 So they blow intermittently
till the true Etesiae come on again at the summer solstice： for from
that time onwards the wind tends to blow continuously。） But the
south wind blows from the tropic of Cancer and not from the
antarctic region。
There are two inhabitable sections of the earth： one near our upper；
or nothern pole； the other near the other or southern pole； and
their shape is like that of a tambourine。 If you draw lines from the
centre of the earth they cut out a drum…shaped figure。 The lines
form two cones； the base of the one is the tropic； of the other the
ever visible circle； their vertex is at the centre of the earth。 Two
other cones towards the south pole give corresponding segments of
the earth。 These sections alone are habitable。 Beyond the tropics no
one can live： for there the shade would not fall to the north； whereas
the earth is known to be uninhabitable before the sun is in the zenith
or the shade is thrown to the south： and the regions below the Bear
are uninhabitable because of the cold。
（The Crown； too； moves over this region： for it is in the zenith
when it is on our meridian。）
So we see that the way in which they now describe the geography of
the earth is ridiculous。 They depict the inhabited earth as round； but
both ascertained facts and general considerations show this to be
impossible。 If we reflect we see that the inhabited region is
limited in breadth； while the climate admits of its extending all
round the earth。 For we meet with no excessive heat or cold in the
direction of its length but only in that of its breadth； so that there
is nothing to prevent our travelling round the earth unless the extent
of the sea presents an obstacle anywhere。 The records of journeys by
sea and land bear this out。 They make the length far greater than
the breadth。 If we compute these voyages and journeys the distance
from the Pillars of Heracles to India exceeds that from Aethiopia to
Maeotis and the northernmost Scythians by a ratio of more than 5 to 3；
as far as such matters admit of accurate statement。 Yet we know the
whole breadth of the region we dwell in up to the uninhabited parts：
in one direction no one lives because of the cold； in the other
because of the heat。
But it is the sea which divides as it seems the parts beyond India
from those beyond the Pillars of Heracles and prevents the earth
from being inhabited all round。
Now since there must be a region bearing the same relation to the
southern pole as the place we live in bears to our pole； it will
clearly correspond in the ordering of its winds as well as in other
things。 So just as we have a north wind here； they must have a
corresponding wind from the antarctic。 This wind cannot reach us since
our own north wind is like a land breeze and does not even reach the
limits of the region we live in。 The prevalence of north winds here is
due to our lying near the north。 Yet even here they give out and
fail to penetrate far： in the southern sea beyond Libya east and
west winds are always blowing alternately； like north and south
winds with us。 So it is clear that the south wind is not the wind that
blows from the south pole。 It is neither that nor the wind from the
winter tropic。 For symmetry would require another wind blowing from
the summer tropic； which there is not； since we know that only one
wind blows from that quarter。 So the south wind clearly blows from the
torrid region。 Now the sun is so near to that region that it has no
water； or snow which might melt and cause Etesiae。 But because that
place is far more extensive and open the south wind is greater and
stronger and warmer than the north and penetrates farther to the north
than the north wind does to the south。
The origin of these winds and their relation to one another has
now been explained。
6
Let us now explain the position of the winds； their oppositions；
which can blow simultaneously with which； and which cannot； their
names and number； and any other of their affections that have not been
treated in the 'particular questions'。 What we say about their
position must be followed with the help of the figure。 For
clearness' sake we have drawn the circle of the horizon； which is
round； but it represents the zone in which we live； for that can be
divided in the same way。 Let us also begin by laying dow