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OUR PHYSICAL WORLD 



multiplication of creature comforts; one must suffice here. 

 Primitive man used chipped-stone implements because he did 

 not know how to obtain anything better. Our American Indians 

 used copper to some extent. They found bits of float copper 

 brought by the glaciers from the great deposits in northern 

 Michigan or in similar locations, and fashioned an occasional spear 

 head or knife from it, but the Indian was still largely in the 

 stone-implement stage when Columbus came to this shore. 

 There came a time when early man learned how to extract the 



FIG. 62. A weather map of the United States 



metals from their ores. That was so very long ago we do not 

 know what his methods were. But following the man of the 

 chipped-stone age and of the polished-stone age, there came 

 peoples who made bronze utensils, and that time is known as the 

 Bronze Age. Bronze is made by melting together tin and copper. 

 So those people must have know how to extract tin from its ores. 

 We know the tin mines of Cornwall, England, were worked during 

 Roman times and probably very much earlier. 



Then came the age of iron implements. Some savage tribes 

 have today very crude processes for extracting iron from its ore. 



