THE WREN'S NEST — DUDLEY. 



485 



(«, c, e,) preserve, however, the original features of the hill, and the work of perforation 

 and demolition which has taken place within, can only be judged of by ascending to its 

 summit and looking into the chasms, or still better by traversing the wide and arched 

 vaults from which the limestone has been extracted. Besides that part of the Wren's 

 Nest which rises into a hill, and which has thus been gutted of the richest matter ; 

 its bands of limestone are now worked at a much inferior level, by a tunnel driven 

 from the lowest adjoining ground across the heart of the hill, in making which, the 

 same double bands of limestone on either side of a central nucleus of shale, were passed 

 through as in the upper works 1 . Deep shafts have further been sunk upon the dip of 

 the rock, from various points along as well as below this tunnel, and the limestone is 

 brought up and conveyed to the open country by a subterranean canal. The above 

 section across the Wren's Nest, proves that it is nothing more than an elevated dome, 

 the calcareous summit of which was truncated during a period of elevation, when the 

 harder or calcareous strata forming the crest being snapped asunder, the fragments 

 were removed t)y subsequent denudation. But though an elliptical, elevated mass, the 

 Wren's Nest is not a complete ellipsoid ; for a small portion of the exterior margin is 

 broken down, and being deficient in the usual limestone barrier, a natural ingress at one 

 point is obtained to the interior. This occurs at the western turn of the northern ex- 

 tremity, where the eastern side, called Mons Hill, instead of uniting with the western, 

 subsides and feathers off. (See ground plan above.) When viewed from the south, on 

 the contrary, the east and west sides appear to be confluent in a well-turned arch, 

 forming the boldest part of the hill or that near to the town of Dudley 2 as represented 

 in this sketch 3 . 



103. 



1 My kind friend Mr. Downing of the Priory, to whom I am above all other persons indebted for an ac- 

 quaintance with the structure of the Dudley district, informed me, that when the tunnel was made, the central 

 shale was precisely as represented in the section, p, 484, i. e. a nucleus with a quaquaversal dip. Without his 

 intelligent directions I should have failed in observing some of the most interesting phenomena here recorded. 



2 The view of Dudley, prefixed to this chapter, is taken from this spot, the Castle Hill being seen on the left 

 hand. In the lithograph, the spectator is supposed to be looking to the south ; in the above wood-cut to the 

 north. 



3 This sketch was taken by the Rev. W. Whewell, during a short tour with Professor Sedgwick and myself 

 to Dudley, Wenlock, and the Wrekin, anno 1832. 



3 p 



