DIMINUTION or FOHESTS. 



The changes which the destruction of forests, the clearing 

 of plains, and the cultivation of indigo, have produced within 

 half a century in the quantity of water flowing in on the 

 one hand, and on the other the evaporation of the soil, and 

 the dryness of the atmosphere, present causes sufficiently 

 powerful to explain the progressive diminution of the lake of 

 Valencia. I cannot concur in the opinion of M. Depons * 

 (who visited these countries since I was there) " that to 

 set the mind at rest, and for the honour of science," a sub- 

 terranean issue must be admitted. By felling the trees 

 which cover the tops and the sides of mountains, men in 

 every climate prepare at once two calamities for future gene- 

 rations ; want of fuel and scarcity of water. Trees, by the 

 nature of their perspiration, and the radiation from their 

 leaves in a sky without clouds, surround themselves with an 

 atmosphere constantly cold and misty. They affect the 

 copiousness of springs, not, as was long believed, by a pecu- 

 liar attraction for the vapours diffused through the air, but 

 because, by sheltering the soil from the direct action of the 

 sun, they diminish the evaporation of water produced by 

 rain. When forests are destroyed, as they are everywhere 

 in America by the European planters, with imprudent pre- 

 cipitancy, the springs are entirely dried up, or become less 

 abundant. The beds of the rivers, remaining dry during 

 a part of the year, are converted into torrents whenever 

 great rains fall on the heights. As the sward and moss 

 disappear with the brushwood from the sides of the moun- 

 tains, the waters falling in ram are no longer impeded in 

 their course ; and instead of slowly augmenting the level of 

 the rivers by progressive nitrations, they furrow, during 

 heavy snowers, the sides of the hills, bearing down the 

 loosened soil, and forming sudden and destructive inunda- 

 tions. Hence it results, that the clearing of forests, the 

 want of permanent springs, and the existence of torrents, 

 are three phenomena closely connected together. Countries 



* In his 'Voyage & la Terre Ferme,' M. Depons says, "The small 

 extent of the surface of the lake renders 'mpossible the supposition that 

 evaporation alone, however considerable within the tropics, could remove 

 M much water as the rivers furnish." In the sequel, the author himself 

 seems to abandon what he terms " this occult case, the hypothesis of an 

 aperture." > ttf 



