462 ON THE CONNECTION OF GEOLOGY 



In the Upper Hartz, the most common inclination of 

 the declivities of the mountains is twenty-five degrees ; 

 nor does it usually exceed thirty-three, at which inclina- 

 tion the beech and spruce grow. The greatest declivi- 

 ties at which ground can be advantageously cultivated 

 have an inclination of thirty degrees. 



The roots of vegetables, especially of grasses, shrubs, 

 and trees, are of much importance in supporting the 

 earth upon the declivities of rocks. Care must therefore 

 be taken that the declivities of mountains which are co- 

 vered with turf or wood, be not altogether deprived of 

 these coverings, as sometimes happens in consequence of 

 loosening the turf for agricultural purposes, or of incau- 

 tiously extirpating the wood. In Norway, near Roraas, 

 there occur mountains, destitute of all vegetation, that 

 had formerly been covered with woods, but where now, 

 from the deficiency of soil, no seeds could take root. 

 The same is the case in many parts of the Alps, where, 

 from the irregular long-continued removal of the timber, 

 the sides of mountains which were formerly covered 

 with thick woods, now show nothing but naked rocks. 

 For this reason, in mountainous countries with very steep 

 declivities, the breeding of cattle and planting of woods 

 are often more advantageous than agriculture. In France 

 the greatest inclination of the public roads is limited by 

 law to an angle of four degrees and forty-six minutes : 

 a similar restriction with regard to agriculture might 

 not be without benefit in certain mountainous countries. 



The inclinations of the surface of the solid crust of 

 the earth vary much, according to the different qualities 

 of the rocks ; some having a tendency to form abrupt 

 precipices, others, again, to produce gentle declivities. 



