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



Avon can escape from the plain of Keynsham ; the river however suddenly 

 winds round a little knoll, marked by a farm-house called the Lodge, and 

 plunges itself into a narrow and concealed defile *, from which, after a course 

 of 3 miles, it emerges into the plain of Bristol, shortly afterwards to be again 

 engulfed in the defile of Clifton. The cliffs bounding this defile are about 

 100 feet in heiglit, and along the greater part of its extent mantled with wood. 

 At one point, where the river bends rapidly round a long peninsula, the scene 

 presented is of great beauty. 



Near to this point the Brislington brook flows into the Avon from the south, 

 after passing through a ravine of similar character. It rises from the side of 

 Dundry-hill at the junction of the inferior oolite with the lias, and having tra- 

 versed the platform of lias, crosses on the south of Brislington the broad valley 

 which separates that platform from the Pennant. Its more obvious course 

 would have been westward, along this valley, into the plain of Bristol ; and a 

 dam of no great height would still force it in that direction ; but it plunges 

 into a deep chasm excavated through the ridge of Pennant, and by this chan- 

 nel seeks the Avon. 



The extension of this ridge of Pennant to the east and west is concealed by 

 the overlying formations. On the west the red marl extends from St. George's 

 to the plain of Bristol : and on the east, near Hanham, higher grounds of red 

 marl capped by lias cover this coal-grit. At the entrance into the defile of the 

 Avon from the plain of Keynsham, the transition from lias to the Pennant is 

 so abrupt as probably to be occasioned by a fault, which has brought the lias 

 down to its present level, which is that of the subsided mass of lias at Bitton ; 

 and to a similar cause we may ascribe the rapid eastern dip of the lias in the 

 cliff which here skirts the northern bank of the river. Similar disturbances 

 attend the junction of the Pennant and lias on the ascent of the hill connected 

 with this cliff on the upper road from Bath to Bristol ; and they are still more 

 strikingly displaved on the east of Oldlands Chapel, when we come close to 

 the line of the fault extending from the Golden Valley across Bitton-hill. 



The Pennant is again exposed in the vale of the Buoyd, about half a mile 

 above Bitton, to the east of the ridge of lias which caps Bitton-hill, and to 

 the north of the fault of the Golden Valley. It is also found on the continua- 

 tion of the same line reposing on the lower coal-shale in the Newton collieries. 

 The dip of the Pennant, along the line through which we have traced it from 

 the plain of Bristol to Newton, is generally to the south-west; on the north it 

 is bounded by the lower coal-shale ; on the south, in the village of Brislington, 

 it supports the upper coal-shale. 



* The entrance of the defile near the Lodge has been strengthened by an ancient agger. 



