358 Mr. Weaver's Geological Observations on 



of Mendip changes. From its central part, a continuous ridge, with a cor- 

 responding dell on either side, projects to the westward, gradually declining 

 to the vicinity of Sidcot ; where the two dells merge into the valley, that finds 

 an outlet on the south of west, between Crook's Peak and Bleadon hill. 

 North and south of that valley and its eastern dells, are two ridges, with 

 broken escarpments respectively facing the south and north ; while to the west 

 the vale is bounded by Bleadon hill, standing in immediate connexion with 

 the northern ridge. 



§ 40. The nucleus of Mendip consists of the old red sandstone; which oc- 

 cupies the highest part of tl;e range in Black Down, extending from the 

 meridian of Blagdon on the east, to that of Roborough nearly, whence, 

 forming a distinct ridge, it gradually sinks into the vale at Sidcot ; but further 

 west it re-appears in the vale, for the distance of a mile, between Winscombe 

 and Barton. In the more central part of Mendip, the old red sandstone is 

 again seen in Nine Barrow^ Down, and about three miles to the north of 

 Wells, extending in the direction of Chewton Mendip. 



The sandstone of the Black Down range supports on its northern and 

 southern flanks a body of slate-clay, which is succeeded by continuous car- 

 boniferous limestone, all in a conformable position. It is distinctly arched 

 from the west of south to the east of north, being nearly flat in the crown of 

 the arch. The sandstone strata dip, on the northern side, at angles gradually 

 increasing from 7° to 30° and 40°, and lastly, where in contact with the slate- 

 clay on that side, to 47°; but on the southern side they support the slate-clay 

 under an angle of 26° to 40°. The former arrangement may be seen in the 

 ravines connected with the combs of Burrington and Dolborough : the latter, 

 in the bye-road to the east of Winscombe church, and in the ravines on the 

 southern side of Mendip. 



The slate-clay on the northern side dips in general 52° to the east of north ; 

 and that on the southern side apparently 26" to 40" to the west of south. 



The limestone on the north and south of this elevated part of Mendip forms 

 a continuous body, which sweeps round the eastern extremity of the high 

 sandstone ridge, being in that quarter in close contact with it ; but to the 

 west of the meridian of Roborough, the limestone is greatly abrupted and 

 recedes from the sandstone, forming, on the north and south of the inclosed 

 valley, the broken escarpments and the dells already mentioned. On the 

 southern side of the highest part of Mendip, the limestone dips generally 20", 

 at first to the south 35° west, and subsequently to the south 20" west, as far 

 as Cheddar, a distance of three miles; but in the western direction, extending 

 toward Crook's Peak and the southern side of Bleadon hill, the dip is to the 



