matter it must carry away, as it goes from crowded cities to be
purified in the country, we can see how, in even this one way
alone, it is a great blessing to us.

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.