INFLUENCE OF FORESTS ON CLIMATES. 77 



successive falling of their leaves forms a thick layer of humus, 

 which has an uncommon power in attracting and retaining 

 moisture. Their thick canopy of verdure also prevents the 

 rays of the sun from penetrating to the ground, and absorbing 

 its humidity. Thus the soil on which forests stand is constantly 

 saturated with water, and becomes the parent of perennial 

 sources and rills, that spread fertility and plenty far from the 

 spot where they originated. 



The rain-attractive influence of forests did not escape the at- 

 tention of Columbus, who ascribed the frequent showers which 

 refreshed and cooled the air, as he sailed along the coasts of 

 Jamaica, to the vast extent and density of the woods that 

 covered the mountains of that island. On this occasion he 

 mentions in his journal that formerly rain had been equally 

 abundant on Madeira, the Canaries, and the Azores, before their 

 shady forests were felled or burnt by the improvident settlers. 



The wanton destruction of woods has entailed barrenness on 

 countries renowned in former times for their fertility. The 

 mountains of Greece were covered with trees during the great 

 epoch of her history, and the well-watered land bore abundant 

 fruits, and sustained a numerous population. But man reck- 

 lessly laid waste the sources of his prosperity. Along with the 

 woods, many brooks and rivulets disappeared, and ceased to 

 water the parched plains. The rain gradually washed the 

 vegetable earth from the sides of the naked hills, and condemned 

 them to sterility. When the snow of the mountains began to thaw 

 under the warm breath of spring, it was now no longer retained 

 by the spongy soil of the forests, and gradually dissolved under 

 their cover; but, rapidly melting, filled with its impetuous 

 torrents the bed of the rivers, and overflowing their banks, 

 spread ruin and devastation far around. 



Unfortunately, forests when once destroyed are not so easily 

 restored, and it requires many centuries ere the bared mountain 

 side reassumes its pristine vesture of shady woods. First 

 lichens, mosses, and other thrifty herbs, content to feed upon 

 nothing, have to prepare a scanty humus for the reception of 

 more pretentious guests. In course of time some small stunted 

 shrub makes its appearance here and there in some peculiarly 

 favoured spot, and after all requires vast powers of endurance 

 to maintain itself on the niggard soil, exposed to the full enmity 



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