"Fairy Chamber." Meanwhile, the water which drips on to the
floor also leaves some carbonate of lime where it falls, and this
forms a pillar, growing up towards the roof, and often the hanging
stalactites and the rising pillars (called stalagmites) meet in
the middle and form one column. And thus we see that underground,
as well as aboveground, water moulds beautiful forms in the crust
of the earth. At Adelsberg, near Trieste, there is a magnificent
stalactite grotto made of a number of chambers one following
another, with a river flowing through them; and the famous Mammoth
Cave of Kentucky, more than ten miles long, is another example of
these wonderful limestone caverns.

But we have not yet spoken of the sea, and this surely is not
idle in altering the shape of the land. Even the waves
themselves in a storm wash against the cliffs and bring down
stones and pieces of rock on to the shore below. And they help
to make cracks and holes in the cliffs, for as they dash with
force against them they compress the air which lies in the joints
of the stone and cause it to force the rock apart, and so larger
cracks are made and the cliff is ready to crumble.

It is, however, the stones and sand and pieces of rock lying at
the foot of the cliff which are most active in wearing it away.
Have you never watched the waves breaking upon a beach in a
heavy storm? How they catch up the stones and hurl them down
again, grinding them against each other! At high tide in such a
storm these stones are thrown against the foot of the cliff, and
each blow does something towards knocking away part of the rock,
till at last, after many storms, the cliff is undermined and large
pieces fall down. These pieces are in their turn ground down to