MINERALOGY. 415 



bratula and coral genera ; the former supposed to be the 

 representatives of the very first inhabitants created in the 

 first-formed ocean. The third section of the Cambrian 

 group consists of various-colored clay slate earths, with 

 laminated rocks of pure and fine-grained slates, iriterstra- 

 tified with graywacke and silicious conglomerates is often 

 several thousand feet in extent and depth and also con- 

 tains a few corals and terebratulae. 



SECOND CLASS. 



UNSTRATIFIED ROCKS OR MASSIVE IGNEOUS ROCK 

 FORMATION. 



FIRST ORDER. 



PRIMITIVE MOUNTAINS OR ROCKS. 



By the name of primitive mountains are meant those 

 massive elevations which are the consequences of those 

 great upheavals which, proceeding from the heart of the 

 earth, changed its first arrangement and aided materially 

 to give it its present form. Everywhere the strata of. 

 the primary rock formation, no longer occupying their 

 horizontal position, but broken through, distorted, frac- 

 tured or inclined, give striking evidence of the great 

 overthrow. In many places where they have not been 

 exactly ruptured by the upheaving force exerted from 

 below, their immense fragments are irregularly raised 

 up, and on the borders of those huge masses exposed to 

 view, exhibit undeniable proofs of their igneous origin 



