[Illustration: FIG. 23.--Intelligent expression is often lacking in
children with adenoid growths.]
42. How to Build a Fire. Substances differ greatly as to the ease
with which they may be made to burn or, in technical terms, with which
they may be made to unite with oxygen. For this reason, we put light
materials, like shavings, chips, and paper, on the grate, twisting the
latter and arranging it so that air (oxygen in the air) can reach a
large surface; upon this we place small sticks of wood, piling them
across each other so as to allow entrance for the oxygen; and finally
upon this we place our hard wood or coal.
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