IOS THE FAIRY-LAND OF SCIENCE. 
the grit which was rubbed off them was carried 
farther down by the stream. And so in time this 
became a little valley, and as the stream cut it deeper 
and deeper, there was room to clamber along the 
sides of it, and ferns and mosses began to cover 
the naked stone, and small trees rooted themselves 
along the banks, and this beautiful little nook sprang 
up on the hill-side entirely by the sculpturing of 
water. 
Shall you not feel a fresh interest in all the little 
valleys, ravines, and gorges you meet with in the 
country, if you can picture them being formed in this 
way year by year ? There are many curious differences 
in them which you can study for yourselves. Some 
will be smooth, broad valleys, and here the rocks have 
been soft and easily worn, and water trickling down 
the sides of the first valley has cut other channels so 
as to make smaller valleys running across it. In other 
places there will be narrow ravines, and here the rocks 
have been hard, so that they did not wear away 
gradually, but broke off and fell in blocks, leaving 
high cliffs on each side. In some places you will come 
to a beautiful waterfall, where the water has tumbled 
over a steep cliff, and then eaten its way back, just 
like a saw cutting through a piece of wood. 
There are two things in particular to notice in a 
waterfall like this. First, how the water and spray 
dash against the bottom of the cliff down which it 
falls, and grind the small pebbles against the rock. 
In this way the bottom of the cliff is undermined, and 
so great pieces tumble down from time to time, and 
keep the fall upright instead of its being sloped away 
