124 How soil has been made 



Material washed away by the sea from the coast is 

 either deposited on other parts of the coast, or is carried 

 out and laid on the floor of the sea. Thus a thick deposit 

 is accumulating, and if the sea were to become dry this 

 deposit would be soil. This has actually happened in 

 past ages. The land we live on, now dry land, has had a 

 most wonderful history ; it has more than once lain at 

 the bottom of the sea and has been covered with a thick 

 layer of sediment carried from other places. Then the 

 sea became dry land and the sediment became pressed 

 into rock, which formed new soil, but it at once began to 

 get washed away by streams and rivers into new seas, 

 and gave rise to new sediments on the floor of these 

 seas. And so the rock particles have for untold 

 ages been going this perpetual round : they become 

 soil ; they are carried away by the rivers, in time they 

 reach the sea ; they lie at the bottom of the sea while 

 the sediment gradually piles up : then the sea becomes 

 dry land and the sediments are pressed into rocks again. 

 The eating away of the land by water is still going on : 

 it is estimated that the whole of the Thames valley is 

 being lowered at the rate of about one inch in eight 

 hundred years. This seems very slow, but eight hundred 

 years is only a short time in geology, the science that 

 deals with these changes. 



Water does more than merely push the rock particles 

 along. It dissolves some of them, and in this way helps 

 to break up the rock. Spring water always contains 

 dissolved matter, derived from the rocks, some of which 

 comes out as "fur" in the kettles when the water is 

 boiled. 



Rocks are also broken up by other agents. There is 

 nearly always some lichen living on the rock, and if you 



