The Origin of Soil 



its mineral part, while the vegetable genera- 

 tions succeeding each other, beginning with 

 the simplest, constitute the soil. 



Note how in nature the least of creatures 

 fulfils its part and, in proportion to its 

 strength, contributes to the general harmony. 

 The changes of weather, which crumble the 

 hardest rock, are not enough to produce the 

 arable ground ; besides these, vigorous plants 

 are needed which can live on that ungrateful 

 surface — those grasses, mosses and lichens, 

 which wear away the stone. It is by means 

 of these elementary plants, so poor in appear- 

 ance and yet so robust, that the dust of the 

 rocks is enriched with a compost and makes 

 a soil fit to nourish other more delicate plants. 

 It is not in cultivated plains that you will 

 find these close carpets of moss and lichen 

 bravely wearing away the rock ; it is at the 

 tops of the mountains that you can see them 

 at work, encrusted on the firm rock in order 

 to convert it into arable ground. It is from 

 these heights that the soil has gradually 

 descended, swept on by the rain, and has 

 come to fertilise the valleys. The same work 

 is always going on. In mountainous regions 

 the tiniest plants incessantly augment the 

 quantity of arable ground. The threads of 



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