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the plain is bare, and destitute of vegetation, 

 This appearance of sterility is here attributed, as 

 it is every where in the valleys of Aragua, to the 

 cultivation of indigo ; which, according to the 

 planters, is, of all plants, that which most ex- 

 hausts (cansa, ' fatigues') the ground. The real 

 physical causes of this phenomenon would be an 

 interesting inquiry ; since, like the effects of fal- 

 lowing land, and of a rotation of crops, it is far 

 from being sufficiently understood. I shall only 

 observe in general, that the complaints of the 

 increasing sterility of cultivated land become 

 more frequent between the tropics, in proportion 

 as they are near the period of their first breaking 

 up. In a region almost destitute of herbs; 

 where every plant has a ligneous stem, and tends 

 to raise itself as a shrub ; the virgin soil remains 

 shaded either by great trees, or by bushes ; and 

 under this tufted shade.it preserves every where 

 coolness and humidity. However active the 

 vegetation of the tropics may appear, the num- 

 ber of roots, that penetrate into the earth, is not 

 so great in an uncultivated soil ; while the plants 

 are nearer to each other in lands subjected to 

 cultivation, and covered with indigo, sugarcanes, 

 or cassava. The trees and shrubs, loaded with 

 branches and leaves, draw a great part of their 

 nourishment from the ambient air ; and the vir- 

 gin soil augments it's fertility by the decomposi 

 tion of the vegetable substances, which progres- 



