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



cides very nearly with the course of the stream^ which runs eastward from Em- 

 borrow Meer by Nettle Bridge to Mells, and its southern with the road leading- 

 from Oakhill eastward^ by Stoke-lane and Leigh^ to Mells. It is flanked on 

 the north, nearly along its whole extent, by the coal-tract, which reaches from 

 the village of Emborrow, by Nettle Bridge, to Vobster and Mells. The strata 

 of this northern portion of the zone of limestone dip, conformably to those of 

 the old red sandstone, at an angle usually exceeding 45° ; and at the crag of 

 Beck Tor and Hurdlestone wood [PI. XXXII. fig. l.j they plunge rapidly 

 beneath the coal-measures, at an angle varying from 75° to 90° ; at Mells also 

 and Whateley their dip to the north is scarcely less considerable. 



Two circumstances affect the regularity of the stratification of this northern 

 part of the calcareous zone. 



1st. An undulation of the strata brings the old red sandstone to the surface 

 at the head of Emborrow Meer, see PI. XXXII. fig. 2. The low ridge to 

 the north of this denudation, and the higher ridge to the south, present the 

 strata of mountain limestone dipping in opposite directions ; the first ascent of 

 the southern ridge, however, is much concealed by overlying beds of chert, 

 which will be described in our account of the horizontal formations. 



2dly. Two faults, at Vobster near Mells, traverse the coal-measures a little 

 to the north of their junction with the mountain limestone, and ranging paral- 

 lel to the drift of the strata, twice throw up the limestone, and cause it to re- 

 emerge in the midst of the coal-measures. [Plate XXXII. fig. 1. C] The 

 most southern of these faults is seen at Vobster rock, which overhangs the river 

 close to the village of that name : the most northern is along the line of the 

 intended canal, 5 of a mile to the north of the former. The limestone is 

 slightly contorted, but has a general dip to the north of about 60°. The 

 coal-measures are highly contorted, and thrown into the greatest confu- 

 sion. 



The junction of the mountain limestone with the coal-measures between 

 Emborrow and Mells is sometimes concealed by beds of the dolomitic conglo- 

 merate : but in Mells park, near which the conglomerate terminates, the oolite 

 (as we have already mentioned) begins to cover the limestone. 



The second nucleus of old red sandstone commences at the distance of 

 1^ mile from the sandstone of Masberry Castle. Penhill, on the north of 

 Wells, is its highest and most central point. It extends in length from north- 

 east to south-west about 3 miles, and is from ^ to f of a mile broad. From 

 the eastern base of Penhill this ridge suddenly slopes away to the ordinary level 

 of the calcareous table-land at the top of the Mendips. It is surrounded, like 

 the eastern nucleus of sandstone, by a mantle of limestone. On the south. 



