216 



as either tree ; of silicic acid 129.35 kilo, or thirty-seven times the amount of the beech,, 

 and as much as one hundred and forty -three times of the pine. It is not to be forgotten 

 that sulphuric and phosphoric acids are very scarce in any soil. 



The beech, however, requires considerably more lime than wheat, the latter yielding 

 12.93 kilo per acre to 20.29 kilo for the beech. 



Whilst then these trees, and undoubtedly all others, use chiefly these inorganic ele- 

 ments, which appear abundantly in every soil, agriculture robs the soil of its rarest com- 

 ponents. 



We may here adduce the experience of farmers, that the winter crops do not need so 

 much manuring as summer crops, and that the former prosper even on a soil of less min- 

 eral vigour. 



This may be explained by the fact that the winter crops have a longer term of vege- 

 tation, and during the same find more opportunity to supply themselves and assimilate 

 the necessary inorganic elements ; for the summer crops, on the contrary, it is necessary 

 that the soil should be either well manured or easily decomposable. Our woody plants 

 enjoy, like the winter crops, a long term of vegetation, and consequently, can prosper on 

 soils that are slow to decompose. 



We have then, from a theoretical point of view, sufficient reason to maintain that 

 the production of timber is much less dependent, nay almost entirely independent of the 

 mineral composition of the soil. This truth we could easily demonstrate by observations 

 from the practice in Germany, where on the mica sand of the Main plain, and the sea 

 sand of the North G-erman plain, the poorest soils in regard to chemical composition, the 

 finest growths of pine and beech may be found. Whoever has travelled through Saxon 

 Switzerland, will agree that on the sandstone of that region, which forms one of the poor- 

 est soils, in moist situaitions, beech, fir, and spruce, species which require favourable condi- 

 tions of growth, prosper exceedingly. 



That it is not the mineralogic condition of the soil, but rather its humidity, which 

 determines the foi'est growth, may often be observed, when on a soil of the same origin 

 and mineralogical composition you find here a most excellent growth, whilst on the drier 

 portions the growth is considerably retarded and stunted. 



We may claim then, that any soil in its natural condition, ?. e. which has not been 

 used for agricultural purposes, contains suflicient inorganic elements for any timber- 

 growth ; that therefore the change of species observed in this country can hardly be at- 

 tributable to an exhaustation of the soil, but to other causes as we shall see later ; that a 

 change or rotation of crops, though it may be in some cases advisable for financial or even 

 forestal reasons, is not a necessity for a successful forestry, as it is in agriculture, and 

 that, if taking place by itself, it is a sign of mismanagement of the original forest. 



Finding then that the chemical composition of the soil is not of much importance in 

 forestry, it must be its physical condition which determines a more or less prosperous 

 timber growth. And so we find all observations on the continent at least coincide in this 

 result, that the greatest mass of wood and the most regular growth of timber is yielded 

 by a soil which is deep, sufficiently loose and rich with humus, and which at the same 

 time possesses a degree of humidity proportionate to the wants of the species growing 

 thereon. 



To understand the character of a soil it will be necessary to discriminate several 

 strata in the same ; we may call that upper part of the soil which the roots penetrate the 

 surface soil, in opposition to the lower strata or subsoil. These two strata may offisr 

 different relative appearances ; they maybe similar, i. c, either both difficult to penetrate 

 like rock and clay, or else easily permeable like sand, loam, or disintegrated rock ; they 

 may be of different character, when either may be hard or loose ; the commonest case be- 

 ing a hard subsoil below more easily permeable surface soil, as for instance when clay or 

 rock or bog iron stone exists below sand or loam. Of course, these strata do not gener- 

 ally exist in this marked distinction, but in gradual transition, the looseness decreasing 

 with the depth. 



In the subsoil strata the angle of inclination is of importance, as upon it partly de- 

 pends the capacity of the soil to retain water. We discriminate in regard to water a 

 pervious and impervious soil. Thus plastic clay, undisintegrated rock, or a horizontal or 



