South-western Coal District of England. 255 



as agreeing with those of the Golden Valley. A great faulty ranging- east and 

 west to the north of Bitton, affects as well the overlying strata as the coal- 

 measures. It cuts off the collieries of the Golden Valley which lie to the north 

 of itj and passing over the southern extremity of Bitton Hill, an eminence of 

 red marl capped by lias, throws down the beds to the south of it at least 200 

 feet; so that the inferior oolite abuts against the lias and subjacent red marl, 

 which are to the north of it, and the lias has sunk to a level with the plain below. 

 [See PI. XXXII. fig. 2. B.] To the west of Bitton Hill, and a little to the 

 east of Oldlands Chapel, the lias is thrown down to the foot of the escarpment 

 of red marl, and abuts against the coal-measures ; and from the east of Old- 

 lands Chapel to Hanham and the Avon, on the prolongation of the line of 

 fault, the junction of the lias with the coal-formation is abrupt, and the rocks 

 continue subject to great disturbances. This fault is an exception to the 

 general rule, that faults are confined to the inclined strata, and do not extend 

 upwards to the overlying ones. Other instances of the same kind will be 

 noticed in the sequel. 



In the southern coal-tract the coal-seams, though thin, are numerous, 31 

 being distinctly recognised near Nettlebridge. These may be divided into a 

 northern and southern series. The southern and lowest series is worked along 

 the whole length of the Nettlebridge valley from Emborrow to Mells, and is 

 distinguished by two principal seams, the lower called Perrink, the upper Cal- 

 lows*. (See 16th and 17th Coal-sections.) The drift of these seams fromVob- 

 ster to Ashwick is E.N.E. and W.S.W. ; but between Ashwick and Moor- 

 wood it bears suddenly towards the north, conforming throughout to the drift 

 and flexure of the limestone of the Mendip chain. The northern and upper 

 series of coal-seams is worked along a line parallel to that of the southern series 

 and about fths of a mile to the north of it. The principal seam is called the 

 Garden course. (See the Coal-sections from 10 to 15.) The whole of this 

 southern coal-tract, since it is bounded on the south by the millstone grit, 

 which is interposed between the Mendip limestone and the coal-measures, and 

 on the north by the Pennant grit, which ranges through Holcombe and has 

 lately been pierced in a shaft between Chilcompton and Stratton, must un- 

 doubtedly be referred to the lower coal-shale. Both the northern and southern 

 coal-seams present phenomena of the highest geological importance. 



In the meridian of Pitcot, situate a little to the north-east of Nettlebridge, 

 all the strata are vertical, a perpendicular shaft being there sunk in a single 

 bed of coal to the depth of 80 fathoms. To the west of this meridian the strata 

 dip at high angles to the north and north-east, conformably to the limestone ; 



* Most of these seams at Vobster afford good smith's coal. 

 VOL. VI. 2 L 



