COMPOSITION OF SOILS 81 



silicate; that is, it contains the two elements which 

 make sand, combined with another called aluminum. 

 Aluminum is a light metal, much like silver in appear- 

 ance, and much used for manufacturing small articles, 

 such as combs, penholders, etc. The metal aluminum 

 is made from clay. Aluminum, silicon, and oxygen make 



CLAY. 



Clay Is a very soft substance, smooth and almost 

 greasy to the touch. When dry it may be easily pul- 

 verized, falling into a powder as fine as the finest flour. 

 Pure clay, such as the fine grades of kaolin, has no 

 sand or grit in it, and may be easily cut with a knife. 

 When wot it becomes 'sticky like dough or putty, and 

 may be moulded into any desired shape. Kaolin or pure 

 clay is used to manufacture potter}' and chinaware. 



I*i the soil, clay exists as a fine powder, and it is the 

 clay particles that make soil sticky. Clay when once 

 wet dries out slowly, hence b retain wah t. Al 



clay soils retain much water, which evaporates slowly, 

 they are, as a rule, cooler than sandy soils. Clay ami 

 sand have almost opposite effects in a soil. Clay in soils 

 holds water, making the soil cool and moist. It is 

 sticky, and serves to bind the particles of soil together. 

 Sand, on the other hand, holds little moisture, and its 

 presence tends to make the soil warm and dry. Its 

 particles are not sticky; hence sandy soils are loose and 

 easy to work. 



1 XPERTMENT 



Thke tome dean Kind, wet it and mould it into any desired thape. 

 Notice how toon it drift out and crumbim to piece*. Pour water on 

 6 



