134 Roots 



observed in the Black earth of Russia, and again in 

 the mud brought down by the Nile and other rivers : 

 all are distinguished for the fineness of their particles 

 and their thorough mixture. 



Why is it that a block of granite is able to support 

 only a few lichens and mosses ? Chiefly because it is 

 a block, into which roots cannot penetrate. It would 

 not make a really fertile soil even if it were crushed 

 into coarse gravel, but it would grow more than it does 

 now ; and if it were ground to fine powder and kept 

 well watered it would grow even corn — not perhaps 

 good crops, though even granites differ in fertility, but 

 still corn — whereas not a stalk can spring up while the 

 granite remains a block, no matter how diligently it be 

 watered. 



By way of testing this point, an experiment was 

 made with some barley sown in a soil consisting ot 

 pure felspar. Felspar is that one of the three minerals 

 of which granite is composed, which, when finely 

 powdered and washed away, forms beds of clay. In 

 this case it was first only coarsely powdered, and the 

 barley grew to a height of fifteen inches ; moreover, 

 the ears formed, one ear ripened, and two seeds were 

 perfected. In the second instance the felspar was finely 

 powdered, and the stalks were very much stronger. 

 One grew to a height of twenty inches, and perfected 

 four seeds. 



Felspar alone, though a compound of several 

 elements, could not in any case produce a good crop ; 

 for the stiffest clay soils under cultivation have been 

 not only well ground, whether by ice or water, but 

 also mixed besides, and contain sand and other in- 

 gredients. 



