ouring from their mouths were all on one level, at
the top of the granite, and the bottom of the limestone. That was to be
expected; for, as I will explain to you some day, water can make caves
easily in limestone: but never, I think, in granite. But I knew that
besides these cold springs which came out of the caves, there were hot
springs also, full of curious chemical salts, just below the very house
where I was in. And when I went to look at them, I found that they came
out of the rock just where the limestone and the granite joined. "Ah," I
said, "now I think I have Madam How's answer. The lid of one of her
great steam boilers is rather shaky and cracked just here, because the
granite has broken and torn the limestone as it lifted it up; and here is
the hot water out of the boiler actually oozing out of the crack; and the
earthquake I heard last night was simply the steam rumbling and thumping
inside, and trying to get out."

And then, my dear child, I fell into a more serious mood. I said to
myself, "If that stream had been a little, only a little stronger, or if
the rock above it had been only a little weaker, it would have been no
laughing matter then; the village might have been shaken to the ground;
the rocks hurled into the torrent; jets of steam and of hot water, mixed,
it may be, with deadly gases, have roared out of the riven ground; that
might have happened here, in short, which has happened and happens still
in a hundred places in the world, whenever the rocks are too weak to
stand the pressure of the steam below, and the solid earth bursts as an
engine boiler bursts when the steam within it is too strong." And when
those thoughts came into my mind, I was in no humour to jest any more
about "young earthquakes," or "Madam How's boilers;" but rather to say
with the wise man of old, "It is of the Lord's mercies that we are not
consumed."

Most strange, most terrible also, are the tricks which this underground
steam plays. It will make the ground, which seems to us so hard and
firm, roll and rock in waves, till people are sea-sick, as on board a
ship; and that rocking motion (which is the most common) will often, when
it is but slight, set the bells ringing in the steeples, or make the
furniture, and things on shelves, jump about quaintly enough. It will
make trees bend to and fro, as if a wind was blowing through them; open
doors suddenly, and shut them again with a slam; make the timbers of the
fl