Yet even now we have not mentioned many of the beauties
of our atmosphere. It is the tiny particles
floating in the air which scatter the light of the
sun so that it spreads over the whole country and
into shady places. The sun’s rays always
travel straight forward; and in the moon, where there
is no atmosphere, there is no light anywhere except
just where the rays fall. But on our earth the
sun-waves hit against the myriads of particles in
the air and glide off them into the corners of the
room or the recesses of a shady lane, and so we have
light spread before us wherever we walk in the daytime,
instead of those deep black shadows which we can see
through a telescope on the face of the moon.
Again, it is electricity playing in the air-atoms
which gives us the beautiful lightning and the grand
aurora borealis, and even the twinkling of the starts
is produced entirely by minute changes in the air.
If it were not for our aerial ocean, the stars would
stare at us sternly, instead of smiling with the pleasant
twinkle-twinkle which we have all learned to love as
little children.
All these questions, however, we must leave for the
present; only I hope you will be eager to read about
them wherever you can, and open your eyes to learn
their secrets. For the present we must be content
if we can even picture this wonderful ocean of gas
spread round our earth, and some of the work it does
for us.
We said in the last lecture that without the sunbeams
the earth would be cold, dark, and frost-ridden.
With sunbeams, but without air, it would indeed have
burning heat, side by side with darkness and ice,
but it could have no soft light. our planet might
look beautiful to others, as the moon does to us, but
it could have comparatively few beauties of its own.
With the sunbeams and the air, we see it has much
to make it beautiful. But a third worker is wanted
before our planet can revel in activity and life.
This worker is water; and in the next lecture we
shall learn something of the beauty and the usefulness
of the “drops of water” on their travels.
Week 10
LECTURE IV. A DROP OF WATER ON ITS TRAVELS
We are going to spend an hour to-day in following
a drop of water on its travels. If I dip my finger
in this basin of water and lift it up again, I bring
with it a small glistening drop out of the body of
water below, and hold it before you. Tell me,
have you any idea where this drop has been? what changes
it has undergone, and what work it has been doing
during all the long ages that water has lain on the
face of the earth? It is a drop now, but it was
not so before I lifted it out of the basin; then it
was part of a sheet of water, and will be so again
if I let it fall. Again, if I were to put this
basin on the stove till all the water had boiled away,
where would my drop be then? Where would it go?
What forms will it take before it reappears in the
rain-cloud, the river, or the sparkling dew?
