2IO Geology. 



the southern prolongation of that great irregular band of 

 Jurassic rocks, running diagonally across England, from 

 Lyme Regis in Dorset, on the S.W., to Redcar in Yorkshire, 

 on the N.E. As spurs and outlyers of the great Cotteswold 

 range, they present the same peculiar features. The main 

 hne of our escarpment, jagged and indented with promon- 

 tory and valley, faces the N.W., whilst the beds have 

 generally a gentle dip to the S.E. Comparing the heights of 

 our hills with those near Gloucester and Cheltenham, it is 

 found that there is a gradual rise in the elevation of the latter, 

 with a greater development of the Inferior Oohte ; for whereas 

 Lansdown is about 700 feet above mean sea level, Cleve hill 

 near Cheltenham rises to a height of 1093 feet. 



Before entering on the details of the Geology of 

 °° °^' the surrounding hills, it may be well to glance at 

 the importance of the Mendip range, in connection with the 

 physical features of the district. Stretching in a continuous 

 line, nearly E. and W., from Frome to the Bristol Channel, 

 it forms the base of a triangle, of which Tortworth is the 

 apex. The core of these hills consists of Old Red sandstone, 

 forming a saddle back, whence on each side the Carbon- 

 iferous Limestone has been thrown off at angles varying from 

 about 12" to almost the perpendicular. A broken irregular 

 N.E.andS.W.line of this Limestone, with occasional exposures 

 of Old Red, forms the highground overlooking the Severn 

 flats, circling round to the N. at Tortworth, and then extend- 

 ing southwards towards Bath, and most probably continuing 

 beneath the more recent covering of Mesozoic rocks onwards 

 to the Mendip anticlinal on the south. Enclosed within this 

 irregular ring of Palaeozoic rocks, lie the Coal basins of 

 Gloucestershire and Somerset, divided by anticlinal folds 

 into the smaller coal fields of Bristol, Nailsea and Radstock, 



