658 Professor Sedgwick and R. I. Murchison^ Esq., on the 



but the actual breadth of this group, measured on a line at right angles to the mean bearing of 

 the beds, is not more than five or six miles. 



The ascending section commences with the beds of passage above noticed ; but to the south of 

 the Yealm, the prevailing rocks are made up of a light gray and greenish gray chloritic schist, 

 with quartz veins and quartzy concretions, and with subordinate hard arenaceous beds ; and they 

 prevail all the way to Stoke Point, with a steady dip about S.S.E, Several of these beds seem 

 to strike into the cliffs between Stoke Point and Erme Mouth, and are repeated over again ; but 

 south of the Erme there is a steady ascending section for about two miles. In the cliff between 

 the Avon and the moutli of the rivulet that descends from the north side of Ringmore, there are 

 some anticlinal and synclinal lines, which we have attempted to represent in our section (PI. LI. 

 fig. 5.). On the whole, however, the ascending series gains towards the south. Tiie prevailing 

 rock is a fine, greenish gray, and leaden-coloured glossy schist, and the prevailing dip is about 

 S.S.E. or S. by E. Near Fishery the beds exhibit the minute striae which (in certain cases) we 

 have considered as an indication of a second cleavage ; here, however, there is no principal 

 cleavage oblique to the bedding. The same series is also marked by beautiful flutings producing 

 the pseudo stripe. Opposite Borough Island, near Avon Mouth in Bigbury Bay, the contortions 

 are marked by a shattered cliff, with quartz veins and numerous joints ; but further south, to 

 a point about lialf a mile beyond Avon Mouth, there is a steady dip to the south, or south by 

 east. We there meet with a synclinal line, which throws the beds into a trough, and produces 

 a northern dip, that prevails, almost without interruption, to Hope Cove, where the whole group 

 terminates abruptly against a formation of chlorite and mica slate. 



Along the lines of strike, several of the more schistose beds are worked for roofing-slate, not 

 generally of good quality ; and, in all the instances that we saw, the slates are derived from planes 

 parallel to the bedding. Immediately to the north of Hope Cove the beds are hard, quartzose, 

 and dark-coloured; and on approaching the junction, they are altered and shattered, and pene- 

 trated in all directions by quartz veins. The actual junction is not parallel to either formation, 

 but maybe traced, at low water, in broken, zig-zag lines, showing the extreme derangement where 

 the two masses are brought into contact. Tliey seem mutually to wedge into and penetrate one 

 another; and on the south side of the headland forming the junction, is a great mass of black- 

 veined slate notched in among the beds of the older system. 



From the lowest beds of this group to the highest (south of Avon Mouth), there is a breadth of 

 four or five miles, measured on a line perpendicular to the strike. Hence, notwithstanding the 

 contortions above noticed, the thickness of the deposit must be very great, especially when we 

 consider the high mean inclination of the beds, which is greater than tliat of the preceding group. 



The junctions on the Kingsbridge river take place on low ground, and give no new information; 

 but if we follow the strike across the promontory from Hope Cove to Start Bay, we may see the 

 two formations in the cliffs south of Tor Cross. The phenomena are there much more simple than 

 at Hope Cove : neither the upper nor the lower system is unusually mineralized, and there is no 

 confusion in the dip. The lower beds (composed, on that part of the coast, of fine quartzose, 

 chloritic slate), though highly inclined, and in some places contorted, dip regularly towards the 

 beds of the upper argillaceous slates, which also, for a considerable way, dip steadily to the north ; 

 but the immediate contact is unfortunately concealed. 



3. To complete our section, it only remains for us to describe the crystalline group which ex- 

 tends to the extreme southern points of Devon. 



Immediately to the south of the junction at Hope Cove, the crystalline slates are extremely 



