CH. II.] THE ROOT. 121 



Not SO barren soils, for I know many that are 

 nearly the same colour at all times, and some boggy 

 soils that are even darker upon the dry surface than 

 beneath. 



Eveiy one knows the fresh earthy smell peculiar 

 to a fertile soil newly dug. This smell is never 

 given forth by boggy or sandy soils that are baiTen, 

 neither is it emitted by chalk. It does not indeed 

 appear to be perceptibly emitted by any soil not con- 

 taining five per cent, of alumina. It is totally absent 

 from the soil on the most barren portions of Bagshot 

 Heath, and is always most powerful upon the heaviest 

 soils. The smell arises in fact fi'om the alumina. 



I have never known a black sandy soil, containing 

 a multitude of white pebbles, that ever repaid the 

 expense of cultivation; especially if it was on the 

 side of a decli\dty, and, I may add, that all the most 

 fertile soils of England have a specific gravity not 

 exceeding 2.4. I have never yet examined a pro- 

 ductive soil ^ith a specific gravity above 2.5. 



Although a black sandy soil, as last described, 

 is invariably infertile, yet a dark coloured soil, if of 

 con-ect staple, will always bear better crops than one 

 lighter coloured. I know two soils, the specific 

 graxities of which are the same ; they have nearly the 

 same amount of aluminous and decomposing matters, 

 but one has much less silica and has much more 

 chalk in its composition than the other. The chalky 



