--+-----+--+---+-----+------
| | | | |
|

Now look at this figure. It represents a section of a volcano; that is,
one cut in half to show you the inside. A is the cone of cinders. B,
the black line up through the middle, is the funnel, or crack, through
which steam, ashes, lava, and everything else rises. C is the crater
mouth. D D D, which looks broken, are the old rocks which the steam
heaved up and burst before it could get out. And what are the black
lines across, marked E E E? They are the streams of lava which have
burrowed out, some covered up again in cinders, some lying bare in the
open air, some still inside the cone, bracing it together, holding it up.
Something like this is the inside of a volcano.




CHAPTER IV--THE TRANSFORMATIONS OF A GRAIN OF SOIL


Why, you ask, are there such terrible things as volcanos? Of what use
can they be?

They are of use enough, my child; and of many more uses, doubt not, than
we know as yet, or ever shall know. But of one of their uses I can tell
you.

They make, or help to make, divers and sundry curious things, from
gunpowder to your body and mine.