INFLUENCE OF FORESTS 101 



at every point, finds its way in quiet flow to the bottom 

 of the slopes. The forest is in fact a huge sponge which 

 gives up its moisture gradually but steadily. It was 

 my good fortune in Ceylon to be able to give to a 

 class of forest students a practical example of the action 

 of forest in retaining water and gradually giving it out. 

 We were encamped at the foot of a huge mass of gneiss, 

 the larger portion of which was bare, but on a portion 

 of the summit of which was a small clump of forest 

 overhanging a steep slope of rock. A heavy downpour 

 of rain came and the rock streamed with water. After 

 the rain, most of the rock quickly dried, but under the 

 clump of forest a thin stream of water still trickled 

 down, and it continued to trickle down during our stay 

 of a few days at that place. 



If forests have the effect of stopping erosion and 

 of storing water to feed the supply of springs, they are 

 also useful in draining water-logged soils. The most 

 celebrated example of this exists in the Landes of Gascony, 

 where plantations of the maritime pine have altered 

 the character of the country from a fever-stricken waste 

 to a thriving forest region capable of supporting a 

 healthy population, to which the various forest works, 

 especially the extraction of resin for turpentine, provide 

 ample occupation. Similar instances can be found in 

 the plantations of Eucalypti in the Roman Campagna 

 and elsewhere. This is due to the faculty of forests, 

 mentioned earlier in this chapter, of lowering the water- 

 table. 



As screens against violent and drying winds, forests 

 are of great importance, and they are of greater importance 

 still when these winds carry shifting sands before them. 

 I have already mentioned the fixation of invading sand- 

 dunes in Gascony by plantations of pine, and of the 

 natural fixation of others in Kordofan by the Acacia 

 Verek ; and how, on the other hand, deforestation has 

 in many places led to vast tracts in Asia and Africa 

 being smothered by billows of sand. 



Observations made in European forests show that 



