THE WEST INDIAN BRIDGE. 



17 



thousand feet more, witli the production of a narrow gorge having 

 precipitous walls, not yet widened into a mature valley. Channels 

 like that of the Colorado also occur crossing submarine plateaus. 



The short tributaries of these high plateau valleys may be likened 

 to gigantic washouts. Such short, deep valleys commonly form 

 at their heads amphitheaters, which may be a few miles in length, 

 as is illustrated in Plate II. These are sometimes so precipitous 



