510 THE NATic 



MOUNTAIN - BUILDING 

 ON A GRAND SCALE 



The study of the 

 arched block of strata 

 16,000 feet or more in 

 thickness from which 

 the picturesque and 

 impressive mountains 

 and canyons have been 

 carved has resulted in 

 the discovery that the 

 rocks in which the 

 great Bow Valley is 

 excavated form a part 

 of the North American 

 continental beds that 

 were deposited in great 

 fresh-water lakes be- 

 fore the waters of the 

 ocean swept over the 

 continent and began 

 their task of depositing 

 the 12,000 feet or more 

 in thickness of rocks of 

 Cambrian age that now 

 contain the remains of 

 the marine life of that 

 period. 



As the study of the 

 formations developed 

 it was found that in 

 the eastward thrusting 

 of the rocks massive 

 limestones were often 

 crushed and ground 

 into f ragments ; i n 

 other places the thinner 

 beds for 100 feet or 

 more would be folded 

 and crumbled between 

 huge masses of even- 

 bedded limestone that 

 showed no traces of 

 disturbance. In other 

 places a series of beds. 

 1,000 feet or more in 

 thickness, met some ob- 

 stacle which they could 

 not crush or surmount, 

 and were driven up- 

 ward at almost right 

 angles, forming series 

 of sharp, ragged ridges. 

 On the east side of the 



