244 Messrs. Buckland's and Conybeare's Observations on the 



From the termination of this series to the corner where the road suddenly 

 turns eastwards up a lateral defile (a distance of 80 paces), overlying beds of 

 the dolomitic conglomerate occur, and from the road they ascend to the sum- 

 mit of the bank, forming a low cliff along the brow of this part of Durdham 

 Down. From this brow they extend by Redlands to South-mead farm, | of 

 a mile west of Westbury, where lias comes in contact with mountain limestone, 

 and crowns both it and the conglomerate with a ridge of greater elevation. 

 The conglomerate, where the road down the bank intersects it, contains 

 rounded masses of mountain limestone, sometimes of three tons weight. 

 Hollow nodules of quartz, lined with quartz crystals, commonly called Bristol 

 diamonds, and sometimes containing crystallized carbonate of lime and sul- 

 phate of strontia, are found, accompanied by hematitic iron ore, in the lowest 

 part of the conglomerate ; and this is probably the true geological position of 

 these nodules, since they have been found in the greatest quantity to the north 

 of St. Vincent's rocks, in digging the foundations of Harley -place, at the junc- 

 tion of the conglomerate with the limestone. 



At the turn in the road above mentioned, the conglomerate is seen resting on 

 thick beds of mountain limestone. These beds of limestone, extending from 

 No. 142 to No. 158 of Mr. Cumberland, are seen on the towing-path cropping 

 out from beneath the series observed in the bank, at the northern extremity of 

 which they form a low precipice, separated by a narrow lateral defile from the 

 lofty scar of the Great Quarry. The Great Quarry exhibits the beds from 

 No. 159 to No. 196 of Mr. C. inclined at less than 30' to the horizon. If our 

 views respecting the fault be correct, these must be considered as a repetition 

 of the beds in St. Vincent's rocks. An interval of about half a mile, through- 

 out which the bank, though steep, is not precipitous, exhibits the beds from 

 No. 1 96 to No. 258 of Mr. C. At the beginning of this interval another warm 

 spring gushes out, close to which the new Hotwell-house has been built. 



The cliff of the Black rock commences at the end of this interval beyond a 

 deep ravine winding up the bank, and includes from No. 259 to No. 291 of 

 Mr. C. The angle of dip is between 40° and 45°. This cliff is succeeded by 

 woody banks. 



The length of the defile of the Avon, where it traverses the principal beds 

 of mountain limestone, from St. Vincent's rock to the Black rock, exceeds 1^ 

 mile. It does not range exactly at right angles to the bearing of the strata, 

 but a little to the north of it ; so that its length is somewhat greater than that 

 of a directly transverse line. Let us take the length of the latter at 1 mile, 

 and the average angle of dip at 20°, vyhich is below the truth. From these 



