CHAPTER III 



THE SOIL 



ANY part of the surface of the earth in which ordinary 

 plants may grow, or which can be 

 made fit for crops, is called soil. 



The larger part of the earth's sur- 

 face is water; ordinary plants cannot 

 grow in the sea, which of course is 

 not soil. Some of the earth's surface 

 is solid or broken rock ; this part, like- 

 wise, is not a fit place for ordinary 

 plants. 



Rocks are under all soils, every- 

 where ; but soils vary greatly in depth. 

 Soil in level places is usually deeper 

 than on mountains, because the soil 

 FIG. is. Diagram show- washes from the mountains to the 



ing the positions of -,, 



soil, subsoil, and rock Valleys. 



THE ORIGIN OF SOIL 



Weathering. In all towns in the Philippines there 

 are old stone buildings or old stone walls. On these, 

 and in the cracks between the stones, plants are grow- 

 ing ; so there must be soil here. But on a new wall or a 

 new building we can find no plants and no soil. 



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