458 ON THE CONNECTION OF GEOLOGY 



some small pasture plants, may grow in very thin layers 

 of soil, where the larger grasses and pasture plants with 

 longer roots, could not find subsistence ; and that shrubs 

 and trees, with long perpendicular roots, cannot survive in 

 many places, where others with more horizontal roots 

 may thrive. These inferences are proved to be correct 

 by observations in agriculture and forestry generally 

 known. 



Mountainous regions, which are not so elevated but 

 that corn might grow sufficiently well in them, in so far 

 as depends upon the conditions of the air or climate, are 

 yet frequently not adapted for its cultivation, on account 

 of the too near approach of the rock to the surface, or 

 shallowness of the soil, and produce nothing but grasses, 

 and some other pasture plants, among which, however, 

 there is the greatest difference in this respect. Tri/b- 

 lium montanum, for example, can support itself on rocky 

 mountains, where T. pratense could not grow. Hedy- 

 sarum onobrychis grows luxuriantly on the sunny de- 

 clivities of calcareous mountains, where Medicago sativa 

 (Lucern) does not find a suitable station. The cultiva- 

 tion of this excellent pasture plant in some mountain- 

 ous regions, especially where the rocks are calcareous, 

 has not proved so advantageous as might have been ex- 

 pected, because the plants have died out in the course of 

 a few years ; whereas, in proper places, where its very 

 long roots find a sufficient depth of soil, they usually 

 last for a great length of time. 



The vicinity of the rock to the under surface of the ve- 

 getable mould, or the shallowness of the soil, seems to be 

 the principal cause why the Beech grows better on many 

 calcareous mountains than the Oak, which, on the other 



