A Geological Description of the Parish of Portishead. 267 



If, leaving the beach, we ascend the hill, we shall see, from the configura- 

 tion of the ground, the extent of the patches of dolomitic conglomerate. 

 The whole of the hill is composed of old red, which, with a tolerably uni- 

 form dip and bearing, extends from the western margin of the alluvial 

 triangle, up the hill towards Down Gate Farm, a little to the east of the 

 road, along which it is quarried, and forms the summit and all but the 

 south-eastern crest of Portishead Down. 



AVc have thus described the north-western half of the district j let us 

 next consider that to the south-east. 



Ascending from the head of the pill in a westerly direction, by either of 

 the two roads, we shall find ourselves for a short space upon the red marl. 

 Higher up the hill, but underlying the red marl, comes in the dolomite, 

 of wiiich the edge and part of the hill is formed. Beyond this the car- 

 boniferous limestone appears in a thin band, behind which is the old red 

 sandstone. If we then walk in the direction of the Down Gate Farm, keep- 

 ing considerably to the east of the road which has been seen to run upon the 

 old red, we shall be able to trace out the thin band of carboniferous lime- 

 stone, reposing to the north-west upon the old red, and supporting in the 

 contrary direction a buff- coloured dolomitic paste, here slightly inclined 

 from the carboniferous limestone. These points it is diiScult to establish 

 fully in the fields ; but on arriving at the road between the Down Gate 

 Farm and the church, a slight section, which we shall now follow, comes 

 to our assistance. The Down Gate Farm stands upon the upper beds of 

 the old red, which a little to the east of it become highly calcareous, and 

 are well seen passing into carboniferous limestone, in a small quarry near 

 the gate at the head of the lane. This section deserves particular attention, 

 since, besides these intermediate beds, there is found above them a bed of 

 quartz conglomerate, concerning which it is difScult to decide whether it 

 be only a detached bed of the old red, or the representation of the millstone 

 grit. In geological and mineralogical characters it v\ill answer to either j 

 but in the latter case, it must be observed that the bed of limestone is un- 

 usually thin. At the Point, moreover, the millstone grit is altogether 

 wanting ; the pennant reposing immediately on the carboniferous limestone. 



Following the road towards the church, thecarboniferous limestone gradually 

 disappears, and in its place are seen the beds of the dolomitic conglomerate, 

 and new red, dipping at a slight inclination, but in a direction conformable 

 with the limestone beneath. As we proceed along the road, the former 

 beds sink, and tiiose superior to them come into view, until, just before the 

 road bifurcates, traces of the red marl appear. At the bifurcation, these 

 rocks become very nearly vertical, dipping slightly to the carboniferous 

 limestone, and then they suddenly cease, and beds of old red come into 

 view, 'i'hesc beds are extremely thin, much comminuted, and as nearly 

 vertical as possible; and, to judge from the appearance at the junction, it 

 seems as though a sudden change had occurred in the relative level of the 



