10 EXPLAIVATION OF PLATE I. 



Explanation of Letters and Figures used in the references to 

 unstratijied and crystalline Rods in Plate 1. 



a. Granite. b. Sienite. c. Porphyry, 



d. Greenstone. e. Serpentine. f. Basalt, or Trap, 

 g. Trachyte. h. Products of Extinct Volcanoes. 



i. Products of Active Volcanoes. 



a. 1. — a. 3. Mountains of Granite, raised into lofty ridges, 



from beneath Gneiss and Primary Slates. 

 a. 4. Granite intermixed with Gneiss. 

 a. 5. — a. 8. Granite, subjacent to stratified rocks of all 



ages, and intersected by volcanic rocks. 

 a. 9. Granite Veins, intersecting Granite, Gneiss, and 



primary Slate. 

 a. 10. Granite Vein, intersecting Primary and Transition 



rocks, and forming overlying masses at the surface. 



a. 11. Granite Vein intersecting Secondary strata, and 



overlying Chalk.* 



b. Dikes of Sienite. 



b. 1. Overlying masses of Sienite. 



c. Dikes of Porphyry. 



c. 1. Overlying masses of Porphyry. 



d. Dikes of ancient Greenstone. 



d. 1. Overlying masses of the same. The Rocks repre- 



sented by d. and e. often pass into one another. 



e. Dikes of Serpentine. 



e. 1. Overlying masses of Serpentine. 



f. Dikes and intruded subterraneous masses of Basalt. 



f. 1. to f. 7. Masses of Basalt protruded through, and 

 overlying strata of various ages. 



* In the locality quoted in the Explanation of Plates, Vol. II. p. 5, 

 the Granite which comes to the surface over the Chalk, is not covered 

 by Tertiary deposites, as represented in our section, PI. 1. 



