114 
THE FAIRY-LAND OF SCIENCE. 
ground away till they became rounded pebbles, such 
as lie in the foreground of the picture (Fig. 28) ; while 
the grit which was rubbed off them was carried far- 
ther down by the stream. And so in time this be- 
FIG. 28. Ravine worn by water in the side of a hill. 
came 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. 
