28 ON THE SOILS AND SUBSOILS 



sandy loam ; but it also thrives well on loam, on sand (if moist), 

 as in tlie Mark Brandenbur ii Prussia, and on the dark variety 

 of bunter sandstein, which a ears more suited for the oak than 

 the younger sandstone form ons, although these, if sufficiently 

 moist, are capable of rearing fine oak forests. Although the 

 oak prefers a moist, and even thrives on a wet, soil, it will not 

 grow on marshes until they have been drained, and tlien it not 

 imfrequently grows well. 



In hilly districts, the soils arising from the decomposition of 

 most of the formations of the Aozoic and Palaeozoic periods, 

 when not v:anting in depth, favour the growth of the oak. Of 

 these the clayey granite, gneiss, and mica-schist, and the various 

 sandy formations of the Cambrian, Silurian, and Devonian 

 systems yield the best soil. 



Clayey porphyry yields a moist, earthy, comparatively fertile 

 soil, suitable for the oak, not so binding as most clays, which on 

 that account do not favour the oak. Diorite, less speedy of 

 decomposition, and poorer in earthy matter, gives rise to a soil 

 too shallow for the oak. The fresh, strong, clayey soil (contain- 

 ing also a slight percentage of lime), arising from the decompo- 

 sition of diabas, appears too binding for the oak, which here does 

 not remain long healthy. 



The same remark applies to the fertile, strong, fresh, clayey 

 soils yielded by melaphyr {e.g., Ilfeld am Harz) and basalt (e.g., 

 Bromberg am Soiling) ; they appear too binding for the oak, and 

 are frequently shallow. 



The clay slates of the Laurentian and Cambrian systems may 

 form soils of two kinds: — 



1. The softer, blueish varieties decompose easily to a mild clay, 

 comparatively free from stones, but in general not very deep. 



2. The quartzy, greenish-grey varieties decompose slowly, and 

 ffive rise to a loose, stonv, and shallow soil; both are more 

 suited for the Norway spruce than for the deep-rooted oak. 



In the Silurian and Devonian systems we may again notice 

 soils of two kinds : — 



1. The dry, shallow, loose, stony varieties, sometimes loamy, 

 but frequently poor in earthy substance, which are derived from 

 the slowly decomposing slates, are unsuited for the oak ; and 



2. The sandy or loamy, fresh, fertile kinds yielded by the 

 sandstones and the conglomerates containing more earthy matter. 

 These, when not wanting in depth, afford an admirable soil for 

 the oak, which here produces excellent timber. 



The Permian system may also be viewed as mainly giving rise 

 to two entirely different varieties of soil — 



1. The Cowjlovierate consisting of quartz, feldspath, granite, 

 syenite, gneiss, mica-schist, and porphyry, all held in mechanical 

 union by a brownish-red kind of clay, which on decomposition 



