THE PARADOX OF CHOICE 



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Figure 2. Arrays of dislocations shown by etch pits in large, 

 pure single crystals of (o) a mineral, apatite (900X), and (I?) 

 pure antimony (665 x). These reveal certain regions in the lattice 

 where there are no atoms. This appears to be one of the most im- 

 portant studies of our times. It accounts for many properties of 

 metals and also for how liquids can form into crystals. 



57 



