468 ON THE CONNECTION OF GEOLOGY 



which we often see in vineyards. The vine frequently 

 thrives remarkably on the declivities of mountains, in. 

 which it sends its roots among fragments of stones. Ex- 

 perience shows, that the quality of wine is influenced by 

 the different conditions of the stones, among which vines 

 are planted. Albertus Magnus has observed, that the 

 vine thrives well in earth which is mixed with fragments 

 of black roofing slate ; and Humboldt remarks, that the 

 vines which grow upon the mountains of the valley of 

 the Rhine, consisting of black elay-slate, afford an excel- 

 lent wine. At the Cape of Good Hope, also, the vine 

 thrives well in a soil produced by the decomposition of 

 clay-slate, and mixed with fragments of it *. It is pro- 

 bable, that the adaptation of this sort of soil to the cul- 

 tivation of the vine, depends upon its slow conducting 

 power, and upon its rapidly imbibing the rays of the sun, 

 on account of its dark colour, and thus increasing the 

 heat of the ground. 



Hitherto we have only spoken of the proximate in- 

 fluence of rocks upon plants ; but it cannot be denied, 

 that the remote effects which they produce, (inasmuch a& 

 vegetable soil is derived from them, and, therefore, the 

 qualities of this soil depend in a great measure upon their 

 nature,) are of greater importance. 



It is from the rocks which constitute the crust of the 

 earth, that the principal portion of productive soil is de- 

 rived. Although other substances belonging to the ani- 

 mal and vegetable kingdoms, are necessary for the 



Vide Dr Adam of Calcutta's Remarks on the Rocks and Soil of 

 Constantia at the Cape of Good Hope, in an early number of the 

 Edinburgh Philosophical Journal. 



