all the land around in dust, which is now
fertile soil. And long did I puzzle to find out why the water stood in
some craters, while others, within a mile of them perhaps, were perfectly
dry. That I never found out for myself. But learned men tell me that
the ashes which fall back into the crater, if the bottom of it be wet
from rain, will sometimes "set" (as it is called) into a hard cement; and
so make the bottom of the great bowl waterproof, as if it were made of
earthenware.

But what gives the craters this cup-shape at first?

Think--While the steam and stones are being blown out, the crater is an
open funnel, with more or less upright walls inside. As the steam grows
weaker, fewer and fewer stones fall outside, and more and more fall back
again inside. At last they quite choke up the bottom of the great round
hole. Perhaps, too, the lava or melted rock underneath cools and grows
hard, and that chokes up the hole lower down. Then, down from the round
edge of the crater the stones and cinders roll inward more and more. The
rains wash them down, the wind blows them down. They roll to the middle,
and meet each other, and stop. And so gradually the steep funnel becomes
a round cup. You may prove for yourself that it must be so, if you will
try. Do you not know that if you dig a round hole in the ground, and
leave it to crumble in, it is sure to become cup-shaped at last, though
at first its sides may have been quite upright, like those of a bucket?
If you do not know, get a trowel and make your little experiment.

And now you ought to understand what "cone" and "crater" mean. And more,
if you will think for yourself, you may guess what would come out of a
volcano when it broke out "in an eruption," as it is usually called.
First, clouds of steam and dust (what you would call smoke); then volleys
of stones, some cool, some burning hot; and at the last, because it lies
lowest of all, the melted rock itself, which is called lava.

And where would that come out? At the top of the chimney? At the top of
the cone?

No. Madam How, as I told you, usually makes things make themselves. She
has made the chimney of the furnace make itself; and next she will make
the furnace-door make itself.

The melted lava rises in the crater--the funnel inside the cone--but it
never gets to the top. It is so enormously heavy that the sides of the
cone cannot bear its weight, and give way low down. And then, through
ash