400 



the second group reappears immediately under the carboniferous 

 zone, forming a band which gradually thins off, and disappears be- 

 low Cockermouth. 



The unstratified groups are then enumerated as follows : 



1. Granite of Skiddaw Forest, the true mineralogical centre of 

 the whole region. 



2. Carrock Fell syenite, irregularly traversing and overlying the 

 third and fourth stratified groups, and apparently underlying the se- 

 cond. 



3. A great formation on the S.W. side of Cumberland, composed 

 of syenite, porphyry, and granite, which breaks through between the 

 second and third groups, penetrating, traversing, and overlying the 

 third, but never overlying the second. 



4. Shap granite, breaking through, between the first and second 

 great, slaty groups, and cutting off the range of the fossiliferous lime- 

 stone by which they are separated from each other. 



5. Granite veins ; porphyritic dykes, having the relations of the 

 Cornish elvans ; common trap dykes : these are found associated 

 with all the stratified groups. 



Chap. II. — Successive stratified groups. 

 § 1. Greywacke and greywacke-slate. — This group is subdivided as 

 follows, in descending order : 



1 . Coarse greywacke and greywacke-slate, occasionally with or- 

 ganic remains, but with no beds of limestone. 



2. Finer greywacke-slate, thrown into great undulations, but 

 having a prevailing strike about N.E. by E. 



3. A band of calcareous slate and fossiliferous limestone, ranging 

 from the hills north of Dalton to Coniston-water-foot. 



4. A broad zone of greywacke-slate, having generally a strike 

 about N.E. by E. and a dip S.E. by S. at an angle varying from 30° 

 to 45°. From this zone masses of roofing slate are commonly de- 

 rived by a cleavage transverse to the plane of stratification. 



5. Calcareous slate and limestone, ranging from the south-western 

 extremity of Cumberland till it is cut off by the Shap granite. Its 

 range, and the evidence it offers of great dislocations, have been de- 

 scribed in a previous memoir (see pp. 247, 318). 



§ 2. Green slate and porphyry, #c. — This great group, which occu- 

 pies all the highest and most rugged mountains of the region de- 

 scribed in this memoir, is essentially composed of great, tabular 

 masses (having generally the same strike and dip as the lower beds 

 of the preceding group), composed of different modifications of por- 

 phyritic and felspathic rocks, and of quartzose and chloritic slate, 

 all the finer portions being derived from a cleavage transverse to the 

 stratification of the beds. The modifications of the slate are first 

 described, and it is shown that they pass, on one hand, into compact 

 felspathic slate sometimes porphyritic ; on the other, into coarse 

 granular and concretionary slaty masses, and through them into brec- 

 cias, or pseudo-breccias, all these changes being effected without any 

 change of strike or dip. In like manner it is shown that the amor- 

 phous, and even semicolumnar, prismatic, porphyries are not only 



