And then
remember, it is these drops, falling again as rain, which make
the rivers and all the moving water on the earth. So also it is
the heat-waves which make the air hot and light, and so cause it
to rise and make winds and air-currents, and these again give
rise to ocean-currents. It is these dark rays, again, which
strike upon the land and give it the warmth which enables plants
to grow. It is they also which keep up the warmth in our own
bodies, both by coming to us directly from the sun, and also in a
very roundabout way through plants. You will remember that
plants use up rays of light and heat in growing; then either we
eat the plants, or animals eat the plants and we eat the animals;
and when we digest the food, that heat comes back in our bodies,
which the plants first took from the sunbeam. Breathe upon your
hand, and feel how hot your breath is; well, that heat which you
feel, was once in a sunbeam, and has travelled from it through
the food you have eaten, and has now been at work keeping up the
heat of your body.
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