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



limestone. It occupies nearly the whole extent of a long narrow valley, which 

 is overhung at the eastern extremity by the picturesque and precipitous moun- 

 tain-limestone crags of Hartcliff* rocks, and thence extends westward to the 

 head of Brockley Combe. 



The western side of Broadfield Down is the most elevated, and its declivity 

 on that side is the boldest. The valleys which descend towards the west from 

 the summit of the down, are terminated by gorges, resembling in appearance 

 and structure, but on a smaller scale, that of Cheddar cliffs. 



There is a small defile of this kind a little to the west of Barrow . Near the 

 village of Brockley is a second of superior dimensions, extending nearly a mile 

 from east to west, and exhibiting, especially on its northern side, abrupt pre- 

 cipices towering above luxuriant forest-trees. But the most magnificent is 

 that of Cleve or Gobble Combe, extending from near the village of Cleve 

 about 1^ mile eastwards. The mouth of this defile is marked by a very 

 striking conical hill, bearing on its summit a huge calcareous tor, and resem- 

 bling Thorpe Cloud at the entrance of Dove-dale in Derbyshire. Like Brock- 

 ley Combe, this ravine is most precipitous on the northern side, though on the 

 southern there are occasionally some very bold cliffs. This chasm is inferior 

 in magnificence to that of Cheddar only, but surpasses it in one feature, being- 

 clothed with luxuriant woods. 



The second calcareous ridge belonging to the western frontier is that which, 

 under the names of Leigh Down, Durdham Down, and King's Weston Down, 

 is so well known in the neighbourhood of Clifton, where it is traversed by the 

 deep and narrow defile of the Avon. These are the several portions of a cal- 

 careous zone encircling a nucleus of old red sandstone, which reaches from 

 Portishead on the south-west to Westbury on the north-east. 



Leigh Down is that part of the zone which extends from Clevedon on the 

 Bristol Channel to the defile of the Avon at Clifton. It is not continuous with 

 Broadfield Down, but is separated from it by the valley of Nailsea, which is 

 occasioned by an undulation in the limestone strata, and contains a small coal- 

 basin. The upper part of this valley, near Kencot Cross, is contracted to a 

 narrow space, only | of a mile broad, the substrata being concealed in that 

 inter>'al by overlying beds of red marl and lias. Leigh Down is about 11 miles 

 long ; its general line of bearing is from south-west to north-east, and the strata 

 dip more or less accurately in every part of it to the south of their line of bear- 

 ing, on an average at an angle of 30°, but, towards the west, at an angle of 60°. 

 Its breadth, from being ^ mile near Clevedon, increases to 1§ mile at the de- 



* Miscalled Hartley rocks in the Ordnance Survey ; they give the name of Hart-cliff to the 

 hundred in which they are situated. 



