1 1 6 THE FAIRY-LA ND OF SCIENCE. 
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, \\ater 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 mile? 
long, is another example of these wonderful limestone 
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 btones 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 
