50 Conservation Reader 



Will these be replaced when once they have all been used 

 up ? It took Nature a very long time to make coal out of 

 the vegetation which had gathered in some ancient swamp. 

 It took her fully as long to make the oil and gas from the 

 bodies of the little organisms that once Kved in the sea. 



The bodies of the Uttle creatures from which oil is made 

 are still gathering upon the bottom of the sea, and there are 

 many swamps where we find vegetation and peat accumulat- 

 ing. But it is a long story from these substances to oil and 

 coal. I am afraid we should get tired of waiting for Nature 

 to make a new supply. 



Gold, silver, copper, and other minerals, so useful to us, 

 are found in very small quantities scattered throughout 

 most of the solid rocks of the earth. It would be impossible 

 for us to obtain these from rocks, because there is so little 

 in any one place. But Nature has collected a part of them 

 in veins in the rocks. We sink shafts upon these veins and 

 mine the ores. It will be a long time before we shall have 

 mined all there is of these minerals. Because they are so 

 hard to get we are not likely to waste them. But it is quite 

 certain that there is a limit to the supply of mineral treas- 

 ures, and equally certain that they can be renewed either 

 very, very slowly, or not at all. Shall we cause our remote 

 descendants to suffer for our carelessness? 



