660 Professor Sedgwick and R. 1. Murchison, Esq., on the 



meet with the following ascending section: 1st, re<l sandstone and slate; 2nd, red, gray, and 

 leaden-coloured earthy slate, almost passing into shale ; 3rd, red and gray indurated shale and 

 calcareous slate, with organic remains, and passing into the limestone. It is therefore obvious 

 that the great limestone is intimately linked to the lower slaty system. 



On the south side of the great saddle of Mudstone Sands the limestone again appears in the clifFat 

 Sharkham Point with a high southern dip. The beds are confused and contorted by the passage of a 

 great vein of iron that is worked, in the limestone, as far as Upton. A very little south of the iron vein 

 is an interpolated mass or dyke of trap which breaks out, here and there, in some ridges ranging to- 

 wards a point north of South Down. Beyond the trap, the beds of limestone are seen in the cliff with 

 a very rapid dip to the south; but some of them appear to thin off and almost to come to an edge 

 in the line of dip. The scale of our section enables us to represent these phenomena only in a 

 general way. Notwithstanding the confusion on the coast produced partly by the iron vein and 

 trap, the general mass of the limestone from Sharkham Point to Upper Brixham dips uneqivocally 

 south, and so passes under the great slaty group that is expanded towards the mouth of the Dart. 

 From all which we conclude, that the limestone of Berry Head has exactly the same general 

 relations to the slate series of South Devon, as the Plymouth limestone*. 



1. The beds immediately over the limestone of Sharkham Point are made up of a gray glossy 

 slate, dipping at a great angle about south by east. They are succeeded by gray, greenish gray, 

 and variegated soft earthy slate, alternating with sandy red and variegated micaceous flag-stone, 

 which occasionally passes into coarse thick beds. Some of the beds exhibit remarkable contor- 

 tions, and a series of specimens might be selected from them which would be almost identical 

 with a corresponding series from the beds of the first group over the Plymouth limestone. The 

 red sandstone does not, however, here predominate so much as it does near Plymouth. 



The rocks above described prevail as far as Man Sands ; on the south side of which is a soft 

 silky gray slate, exhibiting at one single spot obscure traces of organic remains. This slate is over- 

 laid, near the top of the high cliff going over to Scabbacombe Sands, by coarse arenaceous red 

 rocks, like those above described. But they are again succeeded by a fine soft gray and greenish 

 gray shillat, which, with many changes of texture and with many quartz veins and alternations of 

 quartzose, arenaceous bands, is continued to the mouth of the Dart. On the whole, we think we may 

 place the southern hmit of our present group at Scabbacombe Sands : so defined, it is very nearly 

 the representative of the red arenaceous group, above described, over the Plymouth limestone. 

 It is, however, less perfectly developed than the corresponding Plymouth group, and, though on 

 the same general line of strike, is a little further north, in consequence of a gradual change in the 

 run of the beds. 



The rocks south of Galmpton on the Dart agree in their general character with those of the 

 present group ; the boundary of which may be placed on the north side of Dartmouth, but, from 



* On the north side of Mudstone Sands, the calcareous beds overlying the slates have a distinct 

 slaty cleavage, which does not affect the inferior slates at the top of the cliff. Among some slightly 

 undulating beds, are dip-joints pointing between north and magnetic north ; afterwards the beds 

 have a steady dip about magnetic north ; and the dip-joints, which abound, are exactly magnetic 

 north and nearly vertical. At the same place are magnetic east and west joints (strike-joints), the 

 planes of which are inclined magnetic south, 40°; that is to a point opposite to the dip of the beds, 

 a very usual case. Not far fiom these beds are some masses of very coarse red sandstone, which 

 seem to be subordinate to the earthy slates below this limestone. 



