CLASSIFICATION. 69 
Group 2. Diluvial. — Transported bowlders & blocks, 
gravels, &c. 
" 3. Supercretaceous. — Upper and lower fresh- 
water and marine formations. 
" 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 fassiliferous, — 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. Granitic, — Syenite, granite, &c. 
Primary or primitive rocks are supposed by geolo- 
gists to constitute the fourfdation on which rocks of 
ail 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- 
