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capacity to absorb water, and to retain it for a time. Part of the water 

 thus absorbed penetrates into the ground and becomes available for 

 the feeding of springs while the remainder gradually finds its way 

 into the nearest stream. In this manner well-preserved forests must 

 have a decided effect upon the sustained feeding of springs, and the 

 moderation of sudden floods in rivers." On protection of the soil he 

 says : " Water rushing down a bare slope possesses a great mechanical 

 power, by means of which it loosens the soil, and carries it down hill. 

 In this way landslips are often caused, ravines are formed, and fertile 

 land, situated at the foot of the ravines, may be covered with silt and 

 rendered valueless. Frequently the debris collects in rivers and 

 forms obstructions, which are followed by a diversion of the bed and 

 erosion of fertile lands. The rate at which this process proceeds, de- 

 pends on the geological formation of the surface ; the less binding the 

 soil and the looser the formation, the greater will be the damage. If, 

 on the other hand, such slope is covered with a well-preserved forest, 

 the roots of the trees and the layers of humus keep together and pro- 

 tect the soil against the action of water ; besides the crowns intercept 

 and retain, at any rate for a time, a considerable portion of the water. 

 On the whole, a series of obstacles are opposed to the movement of the 

 water, which reduce its velocity and force, or at any rate divide it into 

 numerous small channels. The beneficial effect of tree vegetation in 

 this respect can be observed in most mountain ranges, and especially 

 in the Alps from France to Austria. Wherever, in those parts, ex- 

 tensive deforestations have taken place, the consequence has been the 

 gradual formation of a series of torrents, in all places where the surface 

 did not consist of hard rock ; the debris brought down has covered 

 more and more fertile land at the base of the torrents, and this 

 evil has grown to such an extent, that not only in France, but 

 also in the other Alpine countries, great efforts are now made to re- 

 afforest the denuded areas at a great outlay. When once the evil has 

 been created immediate afforestation is not possible ; it must be pre- 

 ceded by the construction of dams, dykes, walls, &c , to steady the 

 soil until the young forest growth has had time to establish itself and 

 once more to lay hold of the surface soil." 



"The importance of maintaining a complete cover of vegetation in 

 all such cases was recognised many years ago, so that already in the 

 middle ages so-called " Protection Forests" existed, which the then 

 existing laws protected against devastation." 



"Forests protect the soil not only in the hills, but also in lowlands, 

 wherever it consists of so-called moving or shifting sand, along the 

 sea-coast as well as in the interior of countries. The action in this 

 case is due partly to their moderating the force of the air currents, 

 and partly by keeping the soil together through their roots, by the 

 formation of humus and the retention of moisture. In this way the 

 Landes of France have from a dreary waste, been converted into ex- 

 tensive forests intersected by cultivated fields." 



" Hygienic effects of forests. Forests in forming a substantial part 

 of the vegetation of the earth, are an important agency for the pro- 

 duction of oxygen obtained by the decomposition of carbon dioxide. 

 Direct observations have also shown that forest air (like sea-air) is 



