r^fATEMKNT BV M. MaKSSCHaND, 



219 



descent of the waters to the bottom of the valleys, for it is only very 

 slowly that water retained by hydroscopicity and capillarity quits the 

 substances which they penetrate. Moreover, as the greatest storms 

 of rain never do saturate completely the layer of humus on wooded 

 soils, it is impossible to form torrents on these." 



He states that the effect of gazonnement is to augment the 

 hydroscopicity and capillarity of the surface of the soil, bnt that this 

 is not sufficient to secure the absorption of all the water that falls 

 upon it in a storm of rain, and he sites facts in support of the allegation. 

 The same good effects, he states, are produced to a greater extent by 

 buissonnement, or the planting of bushes, while a layer of humus of 

 great hydroscopicity, produced by the decay of their leaves, co-operates 

 in the production of these good effects ; but he cites evidence that 

 even gazonnement and buissonnement combined have failed to prevent 

 erosion and the formation of torrents. 



But forests produce in a surpassing degree each and all of the 

 effects referred to, as produced in a minor degree by meadows and 

 bush. (I) They form by their detritus a very hydroscopic layer, and 

 in consequence augment the quantity of water retained ; (2) They 

 augment the expansion of surface on which the water falls ; and (3) 

 They augment the capillarity and permeability of the subsoil. 



" I have," says he, " in treating of the permeability of the soil, 

 explained the influence of forests on this. In retaining for some time 

 the water at the surface they augment considerably the quantity which 

 is absorbed, particle by particle, by hydroscopicity and capillarity, for 

 this absorption is slow ; and thus, in a word, the forest tempers the 

 action of rain dashed downwards in a storm, and leads the water gently 

 on to the soil, as if it had fallen in a gentle shower ; and further, it 

 augments, in fine, the permeability of the soil, by keeping the surface 

 unhardened and in sOme sort always open to receive the water which 

 comes slowely from the heavens. 



" I make no mention of the influence of forests in regard to 

 evaporation — in regard to the direct absox-ption of water — and in re- 

 gard to the humidity of the atmosphere, etc. I take up one point of 

 view alone of the torrential management of waters in the high 

 mountains, and these relate to this only indirectly. 



" If a storm of rain beat upon a forest the whole of the water which 

 falls is temporarily retained, all penetrates more or less deeply the 

 soil without flowing on the surface ; and, it may be objected, if the 

 subsoil is impermeable the result will be the same. But the objection 

 is without foundation. 1 shall suppose, what is frequently the case, 



