massive strata breaking up solid bodies of flint, quarts , 
' t 
obsidian, jasper, etc., for implements and carving out huge 
monoliths from the living rock for building and sculpture. 
A study of the American mines and quarries gives us a vivid 
conception of the strength and persistency of the forces that 
underlie human development, and of the difficulties encountered 
by the race in carrying culture upward through the stone age 
to the higher level of the age of metal. The shaping of the 
stone into implements and utensils necessarily followed the worU; 
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of the quarryxnen and the story of the work is clearly told in 
many lands, but America's contributions to the history of this 
most important branch of activity are exceptionally full and 
satisfactory. 
AitCI II Tk C T Hits — Aboriginal architecture in America teaches the' 
initial lessons of the development of this branch of culture 
with exceptional clearness beginning at the lowest stage and 
carrying it up (about [to, the level of the keys cone arch. The 
present period displays a wide range of phenomena representing 
