A Geological Description of the Parish of Portishead. 269 



Having thus completed the geological details of this district, which, 

 though somewhat irksome to the general reader, will, we hope, prove useful 

 to those who may feel disposed to go over the ground for themselves, we 

 shall shortly enumerate the general geological features of the district under 

 consideration. 



I. And first, of the old red sandstone, 



1. We have here three distinct and isolated appearances of the old red ; 

 of these, the principal includes Portishead Down, and the ground between it 

 and the sea. On the north it is partially covered up by the dolomite ; on 

 the north-east it terminates abruptly in a bed of shingle, a patch of alluvial 

 soil, and the dolomite ; and on the whole of its south-eastern frontier its 

 termination is gradual, and it sinks under the carboniferous limestone and 

 limestone shale. 



2. The second patch is of a narrow horse-shoe figure, and forms the 

 gorge and flanks of a hill between Capenor and the church. Towards the 

 north-west its convex border terminates very abruptly against the dolo- 

 mite j but in an opposite direction it is gradually covered up by the con- 

 formable strata of the carboniferous limestone. 



3. The third patch forms the summit of the hill behind the point j it is 

 covered up by the horizontal strata upon three of its sides, but on the 

 fourth, towards the north, it terminates regularly in the lower carboniferous 

 limestone shale. 



II. The rock next in superposition is the carboniferous limestone, which 

 also appears in three detached portions. 



1. Of these, the first commences in a narrow zone on the top of the hill 

 west of the mill, and, gradually increasing in width, extends in a south- 

 westerly direction, reposing every where conformably upon the old red of 

 Portishead Down, and covered up along its whole south-eastern frontier by 

 the dolomitic rocks. 



2. The second portion of carboniferous limestone forms the hill between 

 Capenor and the church, reposing towards the north-west conformably 

 upon the horse-shoe of old red, and covered up in an opposite direction by 

 the dolomite. The external character of this portion is very different from 

 that of the last, and closely resembles the beds under the battery. 



3. The third patch forms the ridge of Portishead Point, the basis of the 

 battery, and the sh;de valley to the soutli of it. On the soutli it reposes 

 on the old red, its shale beds being covered up by the dolomite, which nearly 

 encircles it, covering it up towards the sea, and separating the beds of the 

 battery from the rest. These beds are clearly a part of this last ridge, 

 from the rock of which, however, they differ considerably in external cha- 

 racter ; they terminate abruptly towards the west, against a bank of old 

 red shingle. It should be added, that under the dolomite, towards the 

 sea, the pennant reposes conformably ui)on the limestone, until, on the dia- 



No, 5.— Vol. I. 2 N 



