CLASSIFICATION. 



69 



Group 2. Diluvial. — Transported bowlders & blocks, 

 gravels, &c. 



" 3. Supercretaceous. — Upper and lower fresh- 

 water and marine formations. 



u 4. Cretaceous. — Chalk, green sand, and Weal- 

 den rocks. 



" 5. Oolitic. — The oolites and lias. 



" 6. Red sandstone. — Red marble and sand- 

 stone, magnesian limestone, and red con- 

 glomerates. 



" 7. Carboniferous. — Coal measures, carbonif- 

 erous limestone, and old red sandstone. 



" 8. Graywacke. — Graywacke and graywacke 

 slates. 



" 9. Lowest fossiliferous. — Argillaceous and 

 other slates. 



" 10. Non-fossiliferous stratified. — Mica slate, 

 gneiss, &c. 



Unstratified Rocks. 

 " 1. Volcanic. — Lavas, &c. 

 " 2. Trappean. — Greenstone, basalt, porphyry, 



amygdaloid, &c. 

 " 3. Serpentine. — Diallage rock and serpentine. 

 " 4. Gramme— Syenite, granite, &c. 



Primary or primitive rocks are supposed by geolo- 

 gists to constitute the foundation on which rocks of 

 all the other classes are laid ; and, as we have stated, 

 were so called because they contain no fossil re- 

 mains of animals or vegetables, nor any fragments of 

 other rocks imbedded in them. These rocks are, for 

 the most part, extremely hard, and the minerals of 

 which they are composed are often more or less crys- 

 tallized. They occur in immense masses or beds, 

 forming not only the lowest parts of the earth's sur- 

 face with which we are acquainted, but also, pier- 

 cing through the incumbent rocks, they form the 

 summits of the highest mountains. When, there- 



