The Story-Book of the Fields 



is a mistake. After centuries and centuries 

 a strong growth of oaks, beeches and other 

 great trees will have succeeded in establishing 

 themselves. The air, the snow, the rain and, 

 above all, the frost successively attack the 

 hard surface of the lava, detach tiny morsels 

 and gradually produce a little dust at its 

 expense. On this dust there appear strange 

 and vigorous growths — those white and 

 yellow patches, those vegetable crusts called 

 lichens, which live on the rock. The lichens 

 adhere to the lava, wear it away still more, 

 and die, leaving a small amount of compost 

 consisting of their rotted remains. Now 

 the mosses appear, which perish in their 

 turn and augment the quantity of fertilising 

 matter. Then the ferns come, needing more 

 nourishment. After these a few tufts of 

 grass ; then some brambles and poor shrubs ; 

 so that every year the soil is increased by 

 fresh fragments of the lava and of the com- 

 post left by the generations of plants which 

 have rotted on the spot. Thus in the course 

 of time a stream of lava is covered by a forest. 

 The arable ground which we cultivate has 

 had a similar origin. The barren rocks, hard 

 as they are, reduced to dust by the combined 

 action of water, air and cold, have formed 



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