THE AERIAL OCEAN IN WHICH WE LIVE. 7 1 
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 atmo- 
sphere, there is no light anywhere except just where 
the rays fall. But around 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 stars 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 sun- 
