457 



with comparatively little interruption from Whatley at the eastern 

 extremity of those hills, by way of Downhead, Stoke Lane, Maes- 

 bury Camp, Pen Hill, North Hill near Priddy, and Charterhouse, 

 to Shipham and Rowberrow. Here it takes the form of a true anti- 

 clinal, or series of anticlinals, throwing off the Mountain limestone 

 on its northern and southern flanks. It was within this area, imme- 

 diately adjoining Stoke Lane, that Mr. Charles Moore discovered 

 the presence of Trap rock, throwing nmch additional light on the 

 physical structure of the district. 



On the north-west the Old red sandstone occupies the coast line 

 from Clevedon to Portishead, and it is also ■ extensively exposed 

 between Portbury and Stoke Bishop, a good section being seen in 

 the gorge of the Avon where the members of this Society had the 

 advantage of inspecting it a year or two ago. 



On the extreme north it flanks the coal basin almost continuously 

 from Thornbury by Milbury Heath to Tortworth, and thence by 

 Charfield to Wickwar, where it is lost beneath the secondaiy rocks 

 and is seen no naore on the eastern side of the basin. 



Outcrops of Carboniferous Limestone 

 ■ The Carboniferous Hme-itone exhibits an immense development in 

 this part of England. It occupies a much more extended area than 

 the Old red sandstone, and its outcrops can be traced continuously 

 round the greater part of the basin. It appears to hem it in com- 

 pletely on three sides and partially so on the fourth or eastern side. 

 Beginning at Orchard Leigh, near Frome, and proceeding west- 

 ward through Vallis to the summit of the Mendips, we find the 

 Mountain limestone flanking both sides of that range all the way 

 from Mells to Weston-super-Mare. At Broadfield Down it also 

 presents a large area, but there it would seem to be rather an island 

 of limestone which has been lifted up through the surrounding Goal 

 measures than a portion of the chain forming the margin of the 

 basin. 



On the west its outcrops stretch continuously from Clevedon 

 under Leigh Down, Clifton and JJurdham Down to Henbury, where 

 for a short distance it passes beneath the overlying rocks, but it 

 reappears at Kuole Park and extends through Almondsbury, Crom- 

 hall, and Wickwar to Chipping Sodbury. Beyond we only meet 



