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Dew is produced by the assembling from the air of [particles] which
become productive of this sort of moisture; and also by an exhalation
either from wet areas or areas which have bodies of water (which is the
sort of place where dew is most likely to be produced) followed by their
assembling in the same place and their production of moisture and finally
by its movement to lower regions, exactly as certain such things in our
own experience
certain way because of a certain condition of cold air.
Ice is produced both by the expulsion of the round configuration from
the water and by the compression of the scalene and acute-angled [particles]
which exist in the water; and also by the addition from the outside of such
[particles], which are driven together and so produce solidification in the
water by expelling a certain number of round [particles].
The rainbow occurs as a result of the sun shining on water-laden air;
or as a result of some peculiar coalescence of light and air which will
produce the peculiar properties of these colours, either all [together] or
one type at a time; and again, as a result of the reflection of this light
the neighbouring regions of the air will take on the sort of coloration
which we see because the sun shines on its parts. 110. This presentation
of roundness occurs because the vision observes the distance as [being]
equal from all directions, or [possibly] because the atoms in the air (or
those in the clouds which are derived from the same air) are compressed
in such a way that this compound gives off[the appearance of] roundness.
The halo around the moon is produced because air from all sides
moves towards the moon; or when it evenly restricts [the movement of]
the effluences sent off from it to such an extent that this cloudlike
phenomenon forms around it in a circle and is not interrupted in the
slightest extent; or it restricts [the movement of] the air around it symmet-
rically on all sides so that what is around it takes on a round and dense
formation. 111. And this happens in certain parts either because a certain
effluence forces its way in from outside or because heat occupies passages
suitable for the production of this effect.
Comets occur when, under suitable circumstances, fire is collected in
certain places in the meteorological region at certain intervals of time;
or when from time to time the heavens above us adopt a particular kind
of movement, so that such heavenly bodies make their appearance; or
the [comets] just rush in by themselves at certain times because of some
circumstances and approach the regions where we happen to be and
become prominently visible; and they disappear owing to opposite causes.
- Certain heavenly bodies rotate in place [i.e., those near the pole,
which never set], which occurs not only because that part of the cosmos