DISTRIBUTION IN TIME. 153 



IDEAL SECTION OF THE CRUST OF THE EARTH. 



Fig. 39- 



Post-Tertiary and Recent. 

 Pliocene. 



p Miocene. 

 Eocene. 



Cretaceous. 



Oolitic or Jurassic. 



t> Triassic. 

 Permian. 



Carboniferous. 



Devonian or Old Red Sandstone. 



Silurian. 



Cambrian. 

 Huronian. 



Laurentian. 



