very long? Perhaps not, it was so good; but if I had wanted it for a
keepsake, I could have kept it, sealed as it was, for years and years,
and it would have been just as sweet and fresh as when it was given to
me.

Suppose, instead of keeping it in its bottle, I had poured it out into
a glass. Can you tell me what would have happened to it then?

In a few days little bubbles would have come, one after another, up to
the top of the juice; and soon it would have been all full of bubbles.
What causes the bubbles? Floating all about in the air and sunshine
are tiny specks called _spores_. These are to the tiny _yeast_ plants
what seeds are to other plants. Seeds fall into the ground and grow,
but these yeast spores fall into the grape juice and grow. While they
are growing in the grape juice, they eat what they want from the
juice; and, as they eat, they make bubbles of carbon dioxid,--which,
you remember, forms in our lungs and looks like air,--and of another
substance called _alcohol_. Of course, when they have changed the
juice in this way, it tastes very different. It is then what we call
_fermented_.

_Fermented drinks are harmful_; but some people like bubbling drinks
so much that they leave good fresh grape juice open on purpose to let
the little yeast plants get into it and make it into what we call
_wine_. They treat apple juice in just the same way to make _cider_;
and they even take fresh rye and barley and corn, and mash them up,
and put yeast plants into the mash to ferment them and make them into
_whiskey_ and _beer_. It does seem a pity, doesn't it, to take good
foods like wheat and apples and grapes and make them into these things
that really do us harm if we drink them.