EXPLANATION OF PLATE 1. 6 



A. 10. represents a dyke 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 Granitic Veins, is a second series of 

 irregularly injected rocks, composed of Sienite, Porphyry, 

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

 Primary and Transition formations, and the lower regions 

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

 rious directions, but often forming also overlying masses, 

 in places where these veins have terminated by overflowing 

 at the surface, V. 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 repre- 

 sentation 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 that portion of the section is intended to illustrate. 



* An example of the rare Phenomenon of Granite intruded info 

 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. page 73. 



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

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

 Nauman 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 Lime- 

 stone and Granite are entangled in each other, and irregular por- 

 tions and veins of hard Limestone, with green grains and cretaceous 

 fossils, are here and there imbedded in the Granite. 



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



