122 How soil has been made 



a ford here. But further away, either up or down, the 

 stream was deeper and wider, flowed more slowly, had a 

 muddy bottom, and so was not good for paddling. At 

 one place about a mile away some one had widened 

 out the river to form a lake, but this made the stream 

 flow so slowly (as it was now so much wider) that the 

 silt and clay deposited and the lake became silted up, 

 i.e. it became so shallow that it was little more than a 

 lake of mud. The same facts were brought out at the 

 bend of the river. On its convex side, Fig. 55, the 

 water has rather further to go in getting round the 

 bend than on its concave side B\ it therefore flows 

 more quickly, and carries away the soil of the bank and 

 mud from the bottom. But on its concave side where 

 it flows more slowly it deposits material. There is at 

 the bend a marked diflerence in depth at the two sides. 

 On its convex side the stream is rapid and deep, and 

 scours away the bank ; on its concave side it is slower, 

 shallower, and tends to become silted up. Thus the bend 

 becomes more and more pronounced unless the bank 

 round A is protected (the other bank of course needs 

 no protection) and the whole river winds about just as 

 ►you see in Fig. 56, and is perpetually changing its course, 

 carrying away material from one place, mixing it up 

 with material washed from somewhere else, and then 

 deposits it at a bend or in a pool where it first becomes 

 a mud flat and then dry land. Some, however, is carried 

 out to sea. We need not follow the Stour to the sea ; 

 reference to an atlas will show what happens to other 

 rivers. Some of the clay and silt they carry down is 

 deposited at their mouths, and becomes a bar, gives 

 rise to shoals and banks, or forms a delta. The rest 

 is carried away and deposited on the floor of the sea. 



