48 TALKS ABOUT THE SOIL. 



CHAPTER IV. 



KINDS OF SOILS. 



x. SAND AND CLAY. In making our studies 

 of the rocks as giving some of the materials of soils, 

 we paid no attention to the many different kinds of 

 rocks. Our observations have shown us that soils are 

 largely composed of inorganic matter ; and this matter, 

 we have seen, comes from the rocks. It is important, 

 then, to get from the geologist some general idea of 

 how the rocks are classified. It is not necessary to 

 know the name of every variety of rock, provided we 

 are able to classify them in a general way whenever 

 we see them. 



Get a piece of sandstone, a piece of granite, and a 

 bit of chalk. The sandstone, if not in the fields or 

 hills near your home, can be found at any stone-yard, 

 as it is one of the most common building-stones in 

 this country. Granite is used in all our large cities 

 and towns, for paving-blocks. Do not, however, take 

 the black trap-rocks formerly used so much for paving- 

 stones. Granite used in our streets is usually white in 

 color. If possible, use a microscope, or at least a 

 strong magnifying-glass, in examining these three 

 stones. The granite appears to be formed of crystals 



