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 whick 
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 
G 
