12 Conservation Reader 



or trees. When the rain falls on the ground, their roots hold 

 the soil so firmly that it usually washes away only very 

 slowly. When men first began to cultivate the soil, they 

 paid no attention to the fact that water washes away the 

 loose earth very easily. In this loose earth at the top of the 

 ground is stored most of the food which the plants require. 

 Care of the surface of the ground is, then, another thing 

 which we have to keep in mind. 



Men at first made shelters for themselves from anything 

 that was at hand, such as bark, skins, rock, or earth. When 

 they learned to make sharp-edged tools, they began to use 

 trees. Where it is cold, much wood is required to build 

 warm houses. As the numbers of men increased, they used 

 greater and greater quantities of wood. Wood also proved to 

 be most useful for many other purposes than house building. 

 In order to plant larger fields the trees were cut down or 

 burned off, without thought of doing any harm. In time 

 trees became scarce in many parts of the world and men 

 began to realize that care must be used or the supply of 

 wood might fail them. 



Coal was finally discovered and men said, "Now we have 

 something that will last always, for there must be an inex- 

 haustible amount in the earth beneath our feet. AU that 

 we shall have to do is to dig it out." When men grew wiser 

 they learned that coal must not be used carelessly any more 

 than the other gifts of Nature ; otherwise the supply may 

 give out and leave them with nothing to take its place. 



Himting and fishing continued to be the business of many. 

 They invented destructive weapons with which they were 

 able to kill such large numbers of wild creatures that some 

 kinds disappeared entirely. Fish, also, of which people 



