ADVANTAGES OF PLANTING. 



15 



considered as bearing the same proportion to the 

 trunk and branches, in respect of the nourishment 

 which they require, as the straw of corn bears to the 

 grain. But the manure which cultivated land re- 

 ceives is, in general, little more than the straw 

 which grows on it, after it has served for food or lit- 

 ter to cattle. Ground in wood, then, actually re- 

 ceives, in the annual fall of the leaves, as much en- 

 richment as the farmer bestows on his land under 

 tillage. 



Ground employed in agriculture is exposed, at 

 almost every season of the year, to the full action of 

 the atmosphere, and in the drought and heat of 

 summer much of its strength is evaporated. In land 

 covered with wood the case is entirely different ; as, 

 from the shade afforded by the leaves and branches, 

 very little evaporation takes place. This, then, is 

 another reason that serves, in some measure at least, 

 to explain the seemingly paradoxical fact in ques- 

 tion. For, that evaporation has a very powerful 

 tendency to exhaust land, by drawing off and dissi- 

 pating the more volatile part of the matter, which 

 assists in the process of vegetation, there can be no 

 doubt, when we consider that any kind of dung may 

 be deprived of the greater part of its strength by 

 being long exposed to a dry atmosphere. Nor is it 



