WATER IN THE AIR.
I have told you how water is in motion whenever it can be. It runs
whenever it can get a chance to do it; but it is in motion in another
way, which I will now tell you about.
[Sidenote: From what water goes up into the air.]
You hang out a wet cloth to dry. When it is dry, what has become of the
water that was in it? It has gone somewhere. Where has it gone? It has
flown, like the birds, into the air; but it has gone so quietly that
nobody has seen it go. The little fine particles of the water that I
have told you about have mixed up with the air, and are blown about
with it every where. And so, when you write, as the ink dries on the
paper, the water in it flies off into the air, leaving the dark part of
the ink behind.
There is a great deal of water that is going up into the air in this
way all the time. It goes up from every thing that is wet. After a
shower, the ground, the stones, the houses, the trees, and plants are
all very wet, but in a little time they are dry again. Most of the
water on them has gone up in the air, and is mingled up with it. It
has mingled with it in such a way that you can not see it. The air
is generally as clear with all this water in it as it is when it is
perfectly dry. Even in a bright, clear day, there is a great deal of
water mixed up with the air.
But water goes up into the air not merely from things that appear wet.
You remember that, in Part First, I told you that water is all the
time going out from the pores of the leaves. A great deal of water is
furnished to the air in this way.
[Sidenote: Experiment with the arm and a glass jar.]
Then there is water going up from the skins of animals. Much water goes
from your skin into the air constantly, even when you can not see that
you are perspiring. You can prove this by putting your arm into a glass
jar, and holding it there some time. The inside of the jar will become
covered with the water that comes from the pores of the skin on your
arm. This is like the experiment with leaves noticed on page 77 of Part
First.
[Sidenote: Water in the breath.]
There is water, too, coming out from the lungs of animals and mixing
with the air. It comes from their lungs just as it does from the
leaves, which you know are the lungs of plants. You can see this if you
breathe upon a cold window. The moisture or water that is breathed out
with the air from the lungs gathers upon the glass. In the morning you
often see the panes of the windows in your chamber very wet. All this
water has come from your lungs as you have slept. In a very cold day
the water in your breath freezes upon whatever is about your mouth. You
see the water of the breath of a horse frozen on the hairs about his
mouth.
So you see water is going up into the air all the time from the ground,
the leaves, the animals, and indeed from every thing that is at all
moist. It goes up also in great quantities from seas, rivers, lakes,
etc. Water, then, is always moving. It runs and it flies. It flies up
into the air, and comes down again in the rain to run in the streams.
It is ever going its rounds, going up and coming down, and none of it
ever stays long in one place. The only way in which it can be made to
keep still is to shut it up. Let it be free, and it will soon be gone,
either by running or flying.
[Sidenote: Water in the air seen in fog.]
Commonly the water in the air is not seen, as I have before told you;
but sometimes you can see it. You see it in the breath in a very cold
day. The cold air makes it look like smoke coming out of the mouth. You
see it, too, in the fog. When there is a fog there is a great deal of
water in the air. The reason that you can see it is that the particles
of water are not as finely divided up as when the air is clear. They
are in little companies, as we may say, but there are not enough of
them together to make drops. If they were in companies large enough to
make drops, they would fall to the ground--that is, we should have a
rain.
[Sidenote: A beautiful scene.]
Sometimes the fog is every where; sometimes it hangs only just over
the water. If you are on a very high hill, where you can look off and
see a river in the distance, you can sometimes see in the morning a
line of fog stretching along where the river is, while it is nowhere
else. I once saw a very singular and beautiful scene made by the fog.
I had been out on horseback in the night to visit a sick person. As I
returned, just before sunrise, I saw from a very high hill a thick fog
over all the river below. From the river arose high hills, irregular in
their shape, and on the sides of these hills were houses at different
heights. The lower houses were all so covered by this dense fog that I
could not see them, while those that stood high up on the hills I could
see as plainly as ever. It looked as if a sea had come in while I was
gone on my visit, and had filled up the valley where the river ran, for
the fog rose to the same height on the sides of all the hills. Many
of the houses stood upon the very edge of this sea. The scene was so
beautiful that I waited to see the sun rise upon it. As it rose, it
shone over the tops of the hills, and lighted up this sea of fog, which
it in a little time scattered by its heat.
[Sidenote: Dense fogs often hanging over large cities.]
Very thick fogs often hang over large cities, while all around in the
country the air may be perfectly clear. London is often covered with
such a fog. Sometimes it has been so dense that people could not see
to do any business. It is related that the fog over the city of Paris
was once so thick that persons who went about with torches often ran
against each other, because even lights could not be seen unless they
were very near. And in Amsterdam, in a fog in the year 1790, there were
over two hundred persons drowned by falling in the darkness into the
canals which run through every part of that singular city.
_Questions._--What becomes of the water when a cloth is dried? Tell
about the drying of ink on the paper. Tell about water’s going up in
the air after a shower. Can you commonly see the water that is in the
air? Does water go into the air from things that do not appear wet?
What is said about its going from the skins of animals? Tell about
the experiment with the glass jar. What is said about water’s being
breathed out from the lungs? In what ways do you see this shown? What
is said about water’s being in constant motion? When there is a fog,
why is it that you see the water that is in the air? Tell what is said
about fogs. Tell about the fogs that hang over large cities.