STUDY XI. 2L3 



When thefe trees have once acquired a certain 

 degree of growth and fize, they flifle, by their 

 fhade, thofe thorny plants, which fubfift no longer, 

 except along the fkirts of the woods, where they 

 enjoy air fufficient for their vegetation. But in 

 this iïtuation, fuch plants are ftill going on to ex- 

 tend the empire of their fuperiors, from year to 

 year, over the plains. Thus, the thorny plants 

 are the original cradles of the forefls; and the 

 fcourge of the agriculture of Man, is the bul- 

 wark of that of Nature. 



Man has, however, imitated, in this refpect, the 

 proceffes of Nature ; for if he wifhes to protect the 

 newly fown feeds of his garden, he finds it fre- 

 quently neceflary to cover them with prickly 

 branches of one fort or another. It appears to me 

 probable, that there is not a heath but what, in 

 time, might become a foreft, were their com- 

 moners reftrained from driving their flocks thither 

 to pafture, for the cattle crop the tender (hoots of 

 the trees as fa ft. as they fpring up. This, in my 

 opinion, is the reafon why the declivities of the 

 lofty mountains of Spain, of Perfia, and of many 

 other parts of the World, are not clothed with 

 trees : it is becaufe of the numerous flocks of 

 iheep which are driven thither, in Summer, and 

 which roam over their different chains. I am fully 

 convinced tHat thofe mountains were^.covered, in 



p 3 the 



