The Avon, Bristol. 5 1 1 



that of the Thames and the rivers that flow into the 

 Wash and the Humber. 



One of the best known rivers that enters the estuary 

 of the Severn is the other Avon, which flows through 

 Bath and Bristol. Its physical history, on a small scale 

 almost precisely resembles that of the Rhine between 

 Basle and Bonn. 1 



West of Bristol there is a high plateau of Carboni- 

 ferous Limestone, the flat top of which attains a height 

 of nearly 400 feet above the level of the sea. Through 

 a deep narrow gorge in this limestone (fig. 103) the 

 river flows, between Clifton and Durdham Downs on 

 the east and Leigh Wood on the west, north-west of 

 which it enters the low grounds and finds its way to 

 the estuary of the Severn at King's Road. Above 

 Bristol, north and south of the river, the country 

 consists of a number of isolated flat-topped hills, of 

 which Dundry Hill and the Mendips form conspicuous 

 members, while in the neighbourhood of Bath, Lans- 

 down, Charmy Down, Odd Down all the minor Oolitic 

 plateaux now form portions of what was once a con- 

 tinuous broad tableland with minor undulations. In 

 these regions the Avon takes its rise, swelled by many 

 north-flowing tributaries, one of which, the Chew, rises 

 on the north flank of the Mendip Hills. North of 

 Bath, several minor streams flow into the Avon through 

 beautiful valleys which have been scooped out of 

 the Oolitic plateau, while the Boyd, the Siston, and 

 the Frome pass through the soft undulating grounds 

 of Lias, New Red Marl, and Coal-measures that lie 

 west of the bold Oolitic escarpment between Bath and 

 Wotton-under-edge. Some of these streams rise at 



1 ' On the Physical History of the Rhine,' * Journ. Geol. Society,' 

 1874, A. C. Ramsay. 



