EXPLANATION- OF PLATE I. 5 



A. 10. represents a dike and protruded mass of Granite, 

 intersecting and overlying stratified rocks of the Primary 

 and Transition series. A. 11. represents the rare case of 

 Granite intersecting Red Sandstone, Oolite, and Chalk.* 



Sienite, Porphyry, Serpentine, Greenstone. 



Closely allied to Granite Veins, is a second series of 

 irregularly injected rocks, composed of Sienite, Porphyry, 

 Serpentine, and Greenstone (b. c. d. e.) which traverse the 

 Primary and Transition formations, and the lower regions 

 of the Secondary strata ; not only intersecting them in vari- 

 ous directions, but often forming also overlying masses, in 

 places where these veins have terminated by overflowing 

 at the surface, (b'. c'. d'. e'.) The crystalline rocks of this 

 series, present so many modifications of their ingredients, 

 that numerous varieties of Sienite, Porphyry, and Green- 

 stone occur frequently in the products of Eruptions from a 

 single vent. 



The scale of our Section admits not of an accurate re- 

 presentation of the relations between many of these intruded 

 rocks, and the strata they intersect ; they are all placed, as 



the representation of the injections of Basaltic and Volcanic matter 

 which the portion of the section is intended to illustrate. 



* An example of the rare Phenomenon of Granite intruded into the 

 Chalk formation, in the hill of St. Martin, near Pont de la Fou in the 

 Pyrenees, is described by M. Dufrenoy in the Bulletin de la Societe 

 Geologique de France, Tom. 2. p. 73. 



At Weinbohla, near Meissen in Saxony, Prof. Weiss has ascer- 

 tained the presence of Sienite above strata of Chalk; and Prof. Nau- 

 man states, that, near Oberau, Cretaceous rocks are covered by Granite, 

 and that near Zscheila and Neiderfehre, the Cretaceous rocks rest 

 horizontally on Granite; at both these places the Limestone and 

 Granite are entangled in each other, and irregular portions and veins 

 of hard Limestone, with green grains and cretaceous fossils, are here 

 and there imbedded in the Granite. 



De la Beche. Geol. Manual. 3d Edit. p. 295. 

 1* 



