14 ELEMENTS OF SYLVICULTURE. 



sets in, the earthy particles sink down and leave the 

 roots bare, which then wither up and die. 



Sand is found in a granular state, and forms soils 

 which vary considerably according to the size of the 

 grains. When the sand is very fine, an almost im- 

 palpable powder, it has the same properties as clay, 

 compactness and hygroscopicity being proportional to 

 the fineness of the component particles. But usually, 

 the grains of sand are of sufficient size to form a light 

 soil that allows water to permeate to a great depth, 

 and gives it up again with a remarkable facility. 



Sandy soils then vary very much as to their 

 physical properties ; better suited to vegetation, 

 when fine, even though they be pure, than clay and 

 limestone, they are nevertheless poor soils, incapable 

 of furnishing plants with any nourishment. 



Although clay, limestone, and sand cannot 

 individually form a fertile soil, yet when mixed they 

 yield a rich and excellent soil, because the lime it 

 contains is a source of nourishment, and its physical 

 properties are not exaggerated, and therefore injurious, 

 as is the case with any one of the three soils in its 

 pure state. . 



Whatever be the mineral components of the soil, 

 vegetable mould is sufficient to make it of good 

 quality. For it corrects the excessive stiffness of 

 clay, and the lightness of sand and lime ; it absorbs 

 and retains as much as twice its weight of water, 

 without allowing it to filter through ; it gives back 

 the water more easily than clay, but more slowly 

 than sand and lime ; lastly, by a gradual deposit of 

 carbonaceous matter which is not absorbed, it 



