CHAPTER XIII.

WHY AND HOW WE BREATHE.


~1. An Experiment.~--Let us perform a little experiment. We must have a
small bit of candle, a fruit jar, or a bottle with a large mouth, and a
piece of wire about a foot long. Let us notice carefully what we are
about to do and what happens.

~2.~ We will fasten the candle to the end of the wire. Now we will light
it, and next we will let it down to the bottom of the jar. Now place the
cover on the top of the jar and wait the results. Soon the candle burns
dimly and in a little time the light goes out altogether.

~3.~ What do you think is the reason that the candle will not burn when
shut up in a bottle? A candle uses air when it burns. If shut up in a
small, tight place, it soon uses up so much air that it can burn no
longer. Try the experiment again, and when the candle begins to burn
dimly, take it out quickly. We see that at once the light burns bright
again.

~4.~ Suppose we shut the stove draught tight, what is the result? The
fire will burn low, and after a time it will probably go out. Why is
this? Evidently the stove needs air to make the wood or coal burn, just
as the candle needs air to make it burn.