120 



How soil has been made 



Now put some soil into A, At once the soil is 

 stirred up, the water becomes muddy, and the muddy 

 liquid flows into B, But very soon a change sets in, 

 the liquid in A becomes clear, and only the grit and 

 stones are left in the bottom : all the mud — the clay 

 and the silt — is washed into B, There it stops for a 

 long time, and some of it will never wash out. The 

 liquid flowing into G is clearer than that flowing into 

 B, If you keep on putting fresh portions of soil into A 

 you can keep B always muddy, although A is usually 



Fig. 54. 

 Model of a stream. In Ay where the stream flows quickly, 

 the water is clear and the sediment free from mud. 

 In B, where it flows slowly, the water is turbid and 

 the sediment muddy 



clear. At the end of the experiment look at the sedi- 

 ment in each beaker : in A it is clear and gritty, in B 

 it is muddy. If you can get hold of some sea water put 

 some of the liquid from C into it : very soon this liquid 

 clears and a deposit falls to the bottom, the sea water 

 thus acting like the lime water on p. 20. 



