"
Yes, indeed we can. How delightfully fresh it comes to us as we swing, or
when we are driving fast, or sailing; and how terrible its force is when
the stormy wind rushes past, driving everything before it! It is then we
can understand that the gentle air, which yields to the slightest touch,
may be a very mighty power indeed.
And now I am going to tell you something about the air which may surprise
you. We often say of a thing that it is "as light as air"; but air is not
really light, it is so heavy that it would press upon us and crush us, just
as a great hammer might crush your little finger, only that this heavy
weight of air presses quite evenly everywhere all through our body, within
and without, upward as well as downward, and yields at once when we move,
so that we do not feel its weight.
Just think of the weight of water which lies above a little fish as it
swims far down in the sea. Why is it not crushed by it? Just for the same
reason; the water is all round the fish, as the air in our ocean is all
round us; and it presses so evenly that it cannot be felt in any particular
part.
Another very wonderful thing about the atmosphere is that what we call the
air is made up of two airs, or gases, as different as possible from each
other, but mixed so as to make exactly that particular sort of air which is
fit for us to breathe.
One of these gases, named oxygen, might well be called "life-sustainer"; it
forms about one-fifth of the air we breathe, and is that part of it which
makes our fires burn and our lamps give light, and keeps us and all the
animals alive.
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