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A PLANETS HISTORY
193
their quantitative evaluation is less forthrightly demonstrable. Let me, then, give you an epitome of my investigation of the subject.
Consider a ray of light falling on a surface from the
Adventures of a heat ray.
Sun. A part of it is reflected; that is, is instantly thrown off again. By this part the body shines and makes its show in the world, but gets no good itself. Another part is absorbed; this alone goes to heat the body. Now if the visible rays were all that emanated from the Sun, it would be strictly true, and a
