370 Dr. E. Greenly— 



Structures. 



Bands of breccia, sand, and loam alternate with each other, 

 especially at Holly Lane (Fig. 3), and lenticular, impersistent 

 beds of sand or loam, about a foot in thickness, arc occasionally 

 disclosed within the breccias. But within each baud stratification 

 is absent or very feebly developed. Sometimes, in favourable 

 states of weather, very faint signs of it may be detected in the 

 loams. In the sands, bedding may be seen here and there for 

 a foot or two, but it soon dies out. The breccias are tumultuous, 

 the major axes of their great 5 ft. blocks even being often vertical ; 

 while the isolated blocks in the stony sands are at all kinds of angles. 

 The purer sands, where furthest from the hills, are quite unstratified. 

 One or two settlement-faults, with displacements of a few inches, 

 have been revealed in the course of the quarrying. 



But the most curious character of the fine deposits is the develop- 

 ment of a vertical system of divisional planes. It is most 

 pronounced in the loams, and is present even in the impersistent 

 lenticles. The structure cannot be termed a jointing ; it is too 

 close ; and is better described as a sort of cleavage. For it is so 

 well developed that laminae no thicker than \ in. can be flaked 

 off with the hand, and still thinner ones with a knife. No steady 

 strike is perceptible, and, indeed, it shows a tendency to 

 curve with the curvature of the temporary cliffs, as if potential 

 on all vertical planes within the mass, and developed by the weather, 

 particularly frosty weather. The scanty micas are quite insufficient 

 to account for this remarkable cleavage, but we may ascribe it with 

 confidence to the thin shell-flakes, for they stand at all angles, and 

 where they are most abundant it is most pronounced. 



The loams are sometimes traversed by minute capillary tubes, 

 often containing black specks and streaks of carbonaceous matter, 

 evidently the remains of vegetation, particularly rootlets. Mr. G. E. 

 Male states that calcareous concretions, with diameters ranging from 

 ^ to f in., were not uncommon in the matrix of the ossiferous 

 breccia, and small aggregations of calcite are still frequently to be 

 found in the loams. 



Physical Features of the District. 

 Clevedon is situated at the convergence of two ridges (Fig. 1), each 

 about 270 feet in height, one running westward from Bristol, the 

 other south-westward from Portishead. Both are maijily com- 

 posed of Carboniferous Limestone, dipping rather steeply in 

 southerly directions ; but Old Red Sandstone dips under that of the 

 Portishead ridge, while Coal Measure (" Pennant ") Sandstone is 

 brought by a powerful rupture against the north side of that of the 

 Bristol ridge. Outliers of Triassic (Dolomitic) conglomerate cling 

 to the Palaeozoic rocks, and the lowlands are underlain by Keuper 

 marl and sandstone, which, however, are seldom visible. The 

 Portishead ridge is washed by the Bristol Channel, but the southern. 



