Chap. VI.] WENLOCK BEDS AT DUDLEY. 117 
Phillips to be 280 feet thick. There, in the flexures extending to Ledbury, 
it is admirably exposed, in connexion with the overlying Ludlow formation 
(see section, p. 95). At Woolhope it forms the encircling ridge between 
two parallel valleys, the one in the Wenlock shale, and the other in the 
Ludlow shale (see section, p. 110). In fact its ridge-like character is a 
necessary consequence of the superior hardness of the rock, in relation to 
the adjacent soft, argillaceous masses. 
To the north of the town of Dudley, this limestone rises up into domes 
called the Castle Hill and Wren's Nest, which, with other, smaller elevations, 
have been protruded from beneath the surrounding coal-strata. The Castle 
Hill is in the accompanying woodcut represented to the left hand of the 
spectator, who is standing on the slopes of the Wren's Nest, and looking 
southwards over the town of Dudley to the hills of basalt near Kowley. 
Castle Hill. Kowley Hills, Hagley Hills. 
Dudley, from the Wren's Nest. 
(From a Drawing by Lady Murchison : Sil. Syst. p. 480.) 
As the signs of violent igneous action and dislocations of the strata are 
apparent, both in the subterranean works of this rich mining tract, and 
near the various outbursts of basaltic and trappean rocks which have been 
extruded to the surface (Rowley and Pouk Hills, &c), it is fair to infer 
that these domes were thrown into their inflated and arched form by sub- 
terranean forces of expansion *. The Wren's Nest and Castle Hill thus 
exhibit on each of their opposite sides two courses of a limestone which, 
from its superior quality, has been worked out, first in open quarries and 
afterwards by deep galleries. The annexed diagram, exhibiting a section 
through the Wren's Nest, shows how the two bands of the best limestone, 
* See the account of the igneous rocks of this account of these trap-ropks, in the Geol. Mag. 
district, Sil. Syst. p. 496. First described by Mr, No. xix. p. 23 ; and Keport Brit. Assoc. 1865, Trans. 
Keir and others, and subjected to experiments by Sect. p. 53. The descriptions of these and other 
Mr. Gregory Watt, their subterranean relations phenomena connected with the region around Dud- 
to the strata have since been ably explained by ley are given in detail by Mr. J. Beete Jukes, Ee- 
Mr. Blackwell of Dudley. See also Mr. D. Forbes s cords of the School of Mines, vol. i. pt. 2. p. 237. 
