I.] THE SOIL OP THE FIELD. 43 



acid, but acids produced by decaying vegetables by 

 the roots of the grasses and trees which grow above ; 

 and they dissolve the cement of the rock by chemical 

 action, especially if the cement be lime or iron. You 

 may see this for yourselves, again and again. You 

 may see how the root of a tree, penetrating the earth, 

 discolours the soil with which it is in contact. You 

 may see how the whole rock, just below the soil, has 

 often changed in colour from the compact rock below, 

 if the soil be covered with a dense layer of peat or 

 growing vegetables. 



But there is another force at work, and quite as 

 powerful as rain and rivers, making the soil of alluvial 

 flats. Perhaps it has helped, likewise, to make the 

 soil of all the lowlands in these isles and that is, the 

 waves of the sea. 



If you ever go to Parkgate, in Cheshire, try if you 

 cannot learn there a little geology. 



Walk beyond the town. You find the shore pro- 

 tected for a long way by a sea-wall, lest it should be 

 eaten away by the waves. What the force of those 

 waves can be, even on that sheltered coast, you may 

 judge at least you could have judged this time last 

 year by the masses of masonry torn from their iron 

 clampings during the gale of three winters since. 

 Look steadily at those rolled blocks, those twisted 

 stanchions, if they are there still ; and then ask your- 

 selves it will be fair reasoning from the known to the 

 unknown What effect must such wave-power as that 

 have had beating and breaking for thousands of years 

 along the western coasts of England, Scotland, Ireland? 

 It must have eaten up thousands of acres whole 

 shires, may be, ere now. Its teeth are strong enough, 



