770 



THE WONDERS OF GEOLOGY. Lect. VIII. 



At the distance of about 120 miles from London, an 

 insulated mass of Silurian rocks is protruded through 

 the once overlying Triassic and Carboniferous strata at 

 Walsall, and forms a ridge of hills on the eastern borders 

 of the great Staffordshire coal-field ; while near Dudley, a 

 few miles to the south-west, another range of Silurian 

 hills, produced by a similar upheaval, appears in the midst 

 of the same carboniferous basin ; and near these hills is a 

 mass of volcanic rocks, called Rowley Hill.* 



The town of Dudley is situated partly on the coal- 

 field, and partly on the group of Silurian rocks which 

 constitutes a prominent feature in the physical characters 

 of the landscape. These Silurian deposits rise into an 

 elevated chain of hills, which extends four or five miles 

 diagonally across the coal-basin, in a line from Dudley to 

 Wolverhampton ; the latter town standing on Triassic strata 

 near the western margin of the coal- field. f The aspect 

 of the surface of the country denotes the nature of the 

 sub -soil, for the Triassic districts are generally covered with 

 verdure ; while those of the coal, from the extensive mining 

 operations every where in progress, present for the most 

 part a character of sterility and desolation. 



In the Dudley Silurian range, three hills are strikingly 

 conspicuous, namely Sedgley, which is composed of the 

 Upper Ludlow rock and Aymestry limestone ; and the 

 Wren's Nest, and the Castle Hill, consisting of Wenlock 

 shale and limestone; these hills, with their connecting 

 valleys, form a verdant tract in the midst of the surround- 

 ing coal-measures. 



The most remarkable eminence of this group is that 

 called the Wren's Nest, which is a steep headland, covered 

 on the top with stunted wood, and presenting the appearance 



* See the beautiful geological map that accompanies Sir R. Murchi- 

 aon's work on the Silurian System. 



t Sec ante, p. 673, for an account of a colliery near Wolverhampton. 





