often making a complete circle, and then, as the water drips from it day by day, it goes on growing and growing till it forms a long needle-shaped or tube-shaped rod, hanging like an icicle.  These rods are called stalactites, and they are so beautiful, as their minute crystals glisten when a light is taken into the cavern, that one of them near Tenby is called the “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 pebbles which serve to batter against the remaining rock.

Professor Geikie tells us that the waves beat in a storm against the Bell Rock Lighthouse with as much force as if you dashed a weight of 3 tons against every square inch of the rock, and Stevenson found stones of 2 tons’ weight which had been thrown during storms right over the ledge of the lighthouse.  Think what force there must be in waves which can lift up such a rock and throw it, and such force as this beats upon our sea-coasts and eats away the land.