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POPULAR SCIENCE MONTHLY 



its burden of sharp sand driven along with great force, he obtains some 

 conception of the efficiency of the tool. Quartz sand is harder than 

 any of the common minerals in the rocks. Hurled by the rushing 

 water against the sides and bed of the river, it cuts out a path through 

 the rocks as a file does through soft iron. 



Volcanic explosions had nothing to do with the making of the canon. 

 If they had, there would be volcanic rock over all the region instead of 

 in isolated patches, and all the topographic forms would be different. 

 The canon is not the result of cracking apart of the earth's crust. If 

 it were, the rock layers would dip away from the canon; opposite sides 

 would not match ; they would lack marks of cutting parallel to the 



Fig. 7. At Dawn in the Canon. 



bedding; their configuration would be independent of alternating hard 

 and soft layers. The extensive cracking and faulting which does exist 

 has been at right angles to the canon and has presented different kinds 

 of rocks for the river to work upon, thus producing variously shaped 

 walls. As the river carves into succeeding strata the crust is weakened 

 and various buttresses sink towards the river. 



Thus all signs lead to the conclusion that fire did not make the 

 canon, nor did wind, nor earthquake, but that it was made by the same 

 agent which in an hour carves tiny channels in a garden after a rain 

 storm. That agent was running water, the water of the Colorado as 

 for unnumbered years it has been flowing from snowy Rocky Mountain 

 ridges to the hot sands which border the Gulf of California. 



