PART 8
VIII. Such are the facts about spring waters. I
will now proceed to speak of rain water and snow
water. Rain waters are the lightest, sweetest, finest
and clearest. To begin with, the sun raises and draws
up the finest and lightest part of water, as is proved
by the formation of salt. The brine, owing to its
coarseness and weight, is left behind and becomes
salt ; the finest part, owing to its lightness, is drawn
up by the sun. Not only from pools does the sun
raise this part, but also from the sea and from
whatever has moisture in it--and there is moisture
in everything. Even from men it raises the finest
and lightest part of their juices. The plainest
evidence thereof is that when a man walks or sits
in the sun wearing a cloak, the parts of his skin
reached by the sun will not sweat, for it draws up
each layer of sweat as it appears. But those parts
sweat which are covered by his cloak or by anything
else. For the sweat drawn forcibly out by the
sun is prevented by the covering from disappearing
through the sun's power. But when the man has
come into a shady place, his whole body sweats
alike, as the sun no longer shines upon it. For this
reason too rain-water grows foul quicker than any
other, and has a bad smell ; being a mixture gathered
from very many sources it grows foul very quickly.
Furthermore, when it has been carried away aloft, and
has combined with the atmosphere as it circles round,
the turbid, dark part of it separates out, changes
and becomes mist and fog, while the clearest and
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lightest part of it remains, and is sweetened as the
heat of the sun produces coction, just as all other
things always become sweeter through coction.
Now as long as it is scattered and uncondensed, it
travels about aloft, but as soon as it collects anywhere
and is compressed into one place owing to
sudden, contrary winds, then it bursts wherever the
most compression happens to take place. For this
is more likely to occur when the clouds, set in
motion and carried along by a wind that allows them
no rest, are suddenly encountered by a contrary
blast and by other clouds.
1 In such cases
the front is
compressed, the rear comes on and is thus thickened,
darkened and compressed into one place, so that the
weight bursts it and causes rain. Such waters are
naturally the best. But they need to be boiled and
purified
2 from
foulness if they are not to have a bad
smell, and give sore throat, coughs and hoarseness to
those who drink them.
Waters from snow and ice are all bad. For, once
frozen, water never recovers its original nature, but
the clear, light, sweet part is separated out and
disappears, while the muddiest and heaviest part
remains. The following experiment will prove it.
Pour by measure, in winter, water into a vessel and
set it in the open, where it will freeze best ; then on
the next day bring it under cover, where the ice will
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melt best ; if, when it is dissolved, you measure it
again you will find it much diminished. This shows
that freezing dries up and causes to disappear the
lightest and finest part, not the heaviest and coarsest,
to do which it has no power. In this way, therefore,
I am of opinion that such waters, derived from snow
or ice, and waters similar to these, are the worst for
all purposes.
