SCIENTIFIC BACKGROUND 



127 



BEADKL) lAiLl 



l;i OCK BETWEEN PARALLEL RIFTS 

 BOUQUET CANYON 



one age may have a characteristic orientation, often 

 different from the trends of others of a different geo- 

 logic age. 



Structural phenomena of this type may be seen on 

 a larger scale in the great mountain systems of North 

 America, such as the Appalachian, Rocky Mountain 

 and the Pacific Ranges. The western side of the conti- 

 nent, in particular clearly shows such a succession of 

 belts of structures of various ages, each with its own 

 individual direction. These are as clearly recorded on 

 the face of nature as if marked on a blackboard with 

 different colored crayons — the belts of one epoch in up- 

 right lines of white ; of another epoch in left diagonals 

 of green ; of another in horizontal lines of red ; and of 

 still another direstion in lines of yellow, and so forth. 

 In some instances, as in those of the Santa Monica and 

 Puente belts, the elongated mountain blocks are not 



