faces. This suggested that such stones had the property of 

 easy breakage in some directions, leading the discoverers 

 to try shattering flints themselves. They thus found that, 

 indeed, a flint could be shaped quite readily into a useful 

 shape by means of judicious blows with another stone — 

 thus the first crude (or Old Stone Age) tools were pro- 

 duced. Later refinements, involving the pressing off of small 

 pieces of flint, gave the nearly perfect tools of the New 

 Stone Age. 



A more advanced type of experiment was the discovery 

 of the use of tree branches as levers for moving heavy 

 boulders. Perhaps several men one day, while moving along 

 a rocky cliff face, dislodged a boulder which fell on and 

 trapped one of their number. Despite all efforts of the in- 

 dividuals pushing together, they were unable to remove the 

 rock to free their companion, so that they were desperate. 

 Then the most intelligent man, noticing a broken-off tree 

 branch nearby, took hold of it as a tool for a renewed 

 attack on the boulder. The branch did not help him any 

 more than before when he pushed the boulder with it, but 

 then he observed the small space below the boulder and 

 thrust the branch into this. Now he found that pushing on 

 the free end of the branch had a much greater effect than 

 before, and the boulder moved slightly. With a tremendous 

 heave at his branch he dislodged the boulder to the amaze- 

 ment of the others. Thus this man discovered the lever, and 

 probably he experimented further with this new kind of 

 tool, using it to roll boulders for fun. To this day levers 

 form essential parts of many of our machines. 



In all the cases discussed in the foregoing, discovery 

 consisted of observation of a natural situation; the need to 

 control that situation to achieve a certain result; attempts 

 at producing the desired result in a way suggested by the 



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