THE TWO GREA T SCULPTORS. 
107 
the earth, and the furrow grew deeper and wider, the 
sides began to crumble when the sun dried up the 
rain which had soaked in. Then in winter, when the 
sides of the hill were moist with the autumn rains, 
frost came and turned the water to ice, and so made 
Fig. 25 
Ravine worn by water in the side of a hill. 
the cracks still larger, and the swollen stream rushing 
down, caught the loose pieces of rock and washed 
them down into its bed. Here they were rolled over 
and over, and grated against each other, and were 
ground away till they became rounded pebbles, such 
as lie in the foreground of the picture (Fig. 25) ; while 
