162 Probable Effects of Vegetation on Climate. 



there is none. " By felling the trees," says Humboldt, as quoted 

 by Balfour, " that cover the tops and sides of the mountains, men in 

 every climate prepare at once two calamities for future generations ; 

 the want of fuel, and a scarcity of water. Trees, by the nature of 

 their perspiration and the radiation from their leaves in a sky with- 

 out clouds, surround themselves with an atmosphere constantly cold 

 and misty. They affect the copiousness of springs, not, as was lonor 

 believed, by a peculiar 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 the water produced by rain. 

 When forests are destroyed, as they are everywhere in America, by 

 the European planters with an imprudent precipitation, 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. The sward and 

 moss disappearing with the brushwood from the sides of the moun- 

 tain, the waters falling in rain, are no longer impeded in their course ; 

 and instead of slowly augmenting the level of the rivers by progres- 

 sive filtration, they furrow during heavy showers the sides of the 

 hills, bear down the loosened soil, and form those sudden inundations 

 that devastate the country. Hence it results that the destructions 

 of forests, the want of permanent springs, and the existence of tor- 

 rents, are three phenomena closely connected together." Dr Duncan, 

 of the Bombay medical establishment, mentions that, within his own 

 experience, the climate at Dapoolie had been much more hot and 

 dry — streams now dry up in December which used to flow till April 

 or May ; and this he attributes to the destruction of trees which 

 formerly clothed the hills, now left barren and desolate by their 

 removal. In the Southern Concan, within the space of fifteen years, 

 the climate has been greatly deteriorated by the diminution of vege- 

 tation, and consequently, of rain. The people of Pinang have 

 memorialized Government against the destruction of their forests, 

 sure that the result by its continuance will be the ruin of the climate. 

 The dreadful droughts which now so frequently visit the Cape de 

 Verd Islands, is avowedly due to the removal of their forests ; in the 

 high lands of Greece, where trees have been cut down, springs have 

 disappeared. The excessive rains around Rio Janeiro, have been 

 modified and reduced by the diminution of the woods. The valley of 

 Aragua, in South America, affords a curious series of examples of 

 diminution of rain by the destruction of trees, and increase of fall by 

 their multiplication. The valley is completely enclosed by high 

 ranges of hills, giving rise to various streams and rivulets, the waters 

 of which form a lake at the extreme end of the valley. The lake has 

 no exit, and its superfluous waters are carried off by evaporation. Be- 

 twixt 1555, when it was described by Oviedo, and 1800, when it was 

 visited by Humboldt, the lake had sunk 5 or 6 feet, and had receded 

 several miles from its former shores, the portion of the basin thus 



