WHAT IS SOIL? 



49 



blood and in this form go to the various cells or units of 

 building material in the body. In addition to this, water 

 is necessary in order to get rid of the wastes of the body. 

 These wastes must also be dissolved in water and carried 

 off in it, so that water plays an important part in our lives. 

 What is soil ? To the average boy and girl brought 

 up in a large city, the word soil does not mean much. 



Sometimes they may | ; } 1 



play on vacant lots or 

 go to the parks where 

 they see dirt or soil, but 

 they come in contact 

 with it less frequently 

 than the country boy to 

 whom soil means hard 

 work. Gardens depend 

 on soil. They must be 

 weeded and attended 

 to. Crops grow in soil. 

 They must be culti- 

 vated. Fruit trees grow 

 in soil. They require much care. To understand what 

 soil really is and how it came to be, we must look back a 

 great many million years. Long ago, we are told, the earth 

 was a great white-hot mass of rapidly revolving material. 

 As this mass cooled the greater part of it became rock. 

 Later the rock, alternately expanding with heat and con- 

 tracting with cold, began to crack and crumble so that 

 little fragments were formed. These pieces were ground 

 up by the action of ice and running water, and the atmos- 

 phere caused them to decay. Gradually this covering of 

 tiny pieces of rock became soil. Examination of beach 



H.-WHIT. CIV. SCI. IN THE HOME 4 



Formation of inorganic soil. (After Black- 

 welder and Barrows.) 



