AGE OF REPTILES. 



259 



Fig. 158. 



rose into existence in this interval the Rocky Mount- 

 ains, the Andes, portions of the Alps, etc. The same up- 

 lifting continued into the next age, so that these mount- 

 ains, and the Himalayas, Pyrenees, Appenines, etc., were 

 then fully raised. The evidence in regard to the rising 

 of mountains during both these periods is twofold. 1st. 

 The rocks of the cretaceous system lie high up on their 

 sides ; 2d. The marine rocks of the tertiary system that 

 is, of the age of Mammals, flank their sides below at a 

 different slope. Take, for example, the Rocky Mount- 

 ains. The cretaceous rocks are found lying sloped high 

 up upon them. This proves that the sea, from whose 

 waters the materials of the cretaceous rocks were depos- 

 ited, stood over the region where these mountains now 

 are, and that these rocks were raised up after the Creta- 

 ceous age had passed. Then the tertiary rocks were de- 

 posited from waters which flowed about the base of the 

 mountains. But how do we know that the raising of 

 them was not completed till some time in the Tertiary 

 age ? If it was completed, the rocks of the tertiary sys- 

 tem would, of course, not be sloped up the sides of the 



