118 How soil has been made 



down into soil which stops where it is unless the rain 

 can wash it away. If there are no cliffs where you live 

 you can see the same kind of action in the banks of the 

 lanes, in a disused quarry, gravel pit or clay pit. Wher- 

 ever a vertical cutting has been made this downward 

 rolling begins and a heap quickly forms, making the 

 vertical cut into a slope. Plants soon begin to grow, 

 and before long it is clear that soil has been made out 

 of the fragments that have rolled down. This process 

 is known as soil formation, but there is another always 

 going on that we must now study. The heap does not 

 invariably lie at the foot of the cliffi If there is a 

 stream, river, or sea at the foot the fragments may be 

 carried away as fast as they roll down : the differences 

 shown in Figs. 52 and 53 between a cliff at the seaside 

 and a cliff inland arise simply in this way. In inland dis- 

 tricts great valleys are in course of time carved out, and 

 at the seaside large areas of land have been washed away. 

 What becomes of the fragments thus carried away 

 by the water ? The best way of answering the question 

 would be to explore one of these mountain streams and 

 follow it to the sea, but we can learn a good deal by a 

 few experiments that can be made in the classroom. 

 We want to make a model stream and see what happens 

 to little fragments of soil that fall into it. 



Fix up the apparatus shown in Fig. 54. The small 

 beaker A is to represent the narrow mountain stream, 

 the larger one B stands for the wide river, and the 

 glass jar C for the mouth of the river or the sea. Run 

 water through them ; notice that it runs quickly through 

 A, slowly through B^ and still more slowly through C : 

 we want it to do this, because the stream flows quickly 

 and the river slowly. 



