80 The soil cmd the plcmt 



exposed for the ordinary cultivated crops. Such land 

 is, therefore, either grass land, moorland, downland or 

 woodland. 



The roots of plants are living and require air. The 

 soil must not be trodden too hard round them or air 

 cannot get in, nor can it if too much water is present. 



Grass can put up with more water and less warmth 

 than most cultivated crops. 



Instances of these facts may be found in going down 

 any hill 500 ft. or more in height : the top is usually wood 

 or waste, being too cold for crops, below this may come 

 grass land, lower still arable land. It is both warmer 

 and moister in the valley (since water runs down hill), 

 and so we can account for the proverbial fertility of 

 valleys. But just near the river, if there is one, the 

 ground may be too wet for crops, and therefore grass is 

 grown. Clay land that is rather too wet to plough is 

 usually left in grass. 



