124 Studies in Forestry [CHAP. vi. 



covering of the uplands, and the hilly tracts, and stretches not 

 yet required for arable land or pasturage. Rain and snow were 

 then more equably precipitated over the soil itself, and were 

 not so apt to be sucked up and retained by a strongly hygro- 

 scopic surface-growth of weeds and mosses, which likewise is 

 exceedingly active in afterwards utilizing and exhausting the 

 supplies of moisture contained in the upper layer of the soil. 

 The aqueous precipitations were, on the other hand, preserved 

 by a good layer of dead foliage and of the humus or mould 

 resulting from their decomposition, and could thus percolate 

 normally into the soil downwards towards the subsoil, so as 

 to maintain a tolerably equable distribution throughout the 

 whole, owing to the effects of gravity being counterbalanced 

 by capillarity. 



Whilst Boussingault has shown in France that, with increase 

 in the area stocked with conifers, a gradual local sinking of 

 the water-level below the soil has taken place, practical sylvi- 

 cultural experience in Germany has also shown that except 

 at high elevations with humid climate extensive plantations 

 of pure Spruce rapidly lead to a marked decrease in the 

 quantity of soil-moisture. And Runnebaum's comparative 

 investigations in 1885 showed that in mixed woods of Scots 

 Pine with Beech the conditions relative to soil-moisture were 

 more favourable for tree-growth than in pure forests of Pine. 

 It is, however, only right to point out that this must to 

 a certain degree be ascribed to the influence exerted on the 

 soil by the good humus or mould formed by the dead foliage 

 of the Beech. 



3. A larger percentage of Timber is available for the higher 

 technical purposes^ at any rate in mixed crops of broad-leaved 

 genera of trees. Many of our more valuable kinds of timber 

 trees are, when once they have passed through the initial stage 

 of pole-forest, so light-demanding, and so dependent on increase 

 of growing-space for the continuation of vigorous growth and 

 further normal development, that they are unable to maintain 



