melts more lime than it can
carry, and drops some of it again, making fresh limestone grain by grain
as it drips from the roof above; and fresh limestone again where it
splashes on the floor below: till if it dripped long enough, the
stalactite hanging from above would meet the stalagmite rising from
below, and join in one straight round white graceful shaft, which would
seem (but only seem) to support the roof of the cave. And out of that
cave--though not always out of the mouth of it--will run a stream of
water, which seems to you clear as crystal, though it is actually, like
the Itchen at Winchester, full of lime; so full of lime, that it makes
beds of fresh limestone, which are called travertine--which you may see
in Italy, and Greece, and Asia Minor: or perhaps it petrifies, as you
call it, the weeds in its bed, like that dropping-well at Knaresborough,
of which you have often seen a picture. And the cause is this: the water
is so full of lime, that it is forced to throw away some of it upon
everything it touches, and so incrusts with stone--though it does not
turn to stone--almost anything you put in it. You have seen, or ought to
have seen, petrified moss and birds' nests and such things from
Knaresborough Well: and now you know a little, though only a very little,
of how the pretty toys are made.

Now if you can imagine for yourself (though I suppose a little boy
cannot) the amount of lime which one of these subterranean rivers would
carry away, gnawing underground centuries after centuries, day and night,
summer and winter, then you will not be surprised at the enormous size of
caverns which may be seen in different parts of the world--but always, I
believe, in limestone rock. You would not be surprised (though you would
admire them) at the caverns of Adelsberg, in Carniola (in the south of
Austria, near the top of the Adriatic), which runs, I believe, for miles
in length; and in the lakes of which, in darkness from its birth until
its death, lives that strange beast, the Proteus a sort of long newt
which never comes to perfection--I suppose for want of the genial
sunlight which makes all things grow. But he is blind; and more, he
keeps all his life the same feathery gills which newts have when they are
babies, and which we have so often looked at through the microscope, to
see the blood-globules run round and round inside. You would not wonder,
either, at the Czirknitz Lake, near the same place, which at