The Soil: Its Use and Abuse 



^357 



Fig. 5. — Micro-photograpk of fine sand soil 

 showing the irregular shape of the particles 

 and their difference in mineral composition. 

 The mineral plant foods are contained in 

 these particles of mineral 



Soil is sometimes called pulverized rock, but it is more. Together with 

 the organic matter of which it is composed, it is the seat of activity of 

 millions of bacteria and of minute 

 thread-like plants, called fungi, 

 that contribute to its productive- 

 ness. 



THE MAKING OF SOIL 



Rain, wind, frost, glacial ice, 

 streams, waves, plants and ani- 

 mals, and the solvent power of 

 water, are at work continually on 

 every exposed rock. By these 

 agencies mountains have been 

 reduced to plains, and lakes, and 

 even oceans, filled to the condition 

 of dry land. We may see these 

 processes in operation by the road- 

 side after a shower of rain, or in 

 the garden, as well as in mountain 

 parks. In the Alps Mountains, in 

 Switzerland, the tops are capped by snow and ice which slide down the 

 gorges with a tremendous grinding force; the ice melts and this great 



volume of water flows away ^with such 

 violence as to furrow the rock slopes and 

 carry away every bit of loose material. 

 Trees and smaller plants pry their roots 

 into the fissiires, and winds send blasts of 

 sand and dust against the ledges. Thus by 

 degrees the mountain of rock becomes a 

 plain of soil. 



One may see these results wherever he 

 is, and may observe the processes that have 

 given rise to them. They may differ in 



Fig. 6.— Micro- photograph of silt magnitude but not in kind. Note how frost 

 soil showing the much smaller size 11 1 j r 1 j r ^ 



of particles The particles are of breaks up clods of clay and even of stone; 



the same general shape and vari- how the rivulets after a rain gully the hill- 



ety in mineral composition as ■ ^ ■, ■, r 1 j 



the sand Owing to its greater Side and leave a mass of gravel or mud 



fineness, the food contained in where the water comes to rest. Then note 

 ..7/ is much more available ^^^ ^^^^^^ ^^^^ ^p^.^^ ^p_ ^^^ ^^^^^^^ ^^^^^ 



roots— how they thread their way about through the spaces in rock and 

 soil, expanding each a little by their growth and search for water and food. 





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