SOIL BUILDERS 7 



less. The simile "immovable as a rock," is 

 not perfect. Even the rock, our common symbol 

 of stability, is subject to the universal law of cnange; 

 it is broken down, re-created and broken down 

 again, over and over, while it fills its place in the 

 working out of the Great Design. 



PLANTS AS SOIL BUILDERS 



Broken rock alone, however, does not make a 

 fertile soil, as the farmer defines fertility. There 

 are plants that thrive on bare rock, but the plants 

 that are grown as farm crops are of a higher order 

 and cannot rough it like this. A fertile soil one 

 that will grow large crops of the higher plants, 

 either wild or cultivated must contain a con- 

 siderabla^mouiiL_QjLhumiis, which is chiefly de- 

 cayed vegetation. A soil made of rock alone may 

 contain all the mineral plant food that farm crops 

 need, but it is apt to lack nitrogen and has not the 

 right texture. ' \ 



The Evolution of a Soil. Nothing in nature is 

 more interesting tnan the gradual evolution of a 

 fertile soil from a barren rock, and nothing is more 

 significant of the illimitable wisdom of the Creator. 

 The history of soil building reads something like 

 this: In the beginning is a lofty cliff, mute witness 

 of the eruptions and disturbances through which 

 the earth passed in cooling. It is bare and deso- 

 late. No living thing finds nourishment upon it. 

 For centuries the storms beat against it; ice, rain 

 and sudden changes in temperature pry off great 

 boulders, which crash into the valleys. In the 

 course of time there come to be upon these boulders, 

 and upon the rocks and stones split off from them, 

 lichens and other humble plants that are able to 



