§ 16. THE MALVERN HILLS. 



779 



longation of that of the Cleat and Abberley Hills, forms 

 the nucleus of the ridge, and appears in the point called 

 Lickey Beacon, on the northern end of the Bromsgrove 

 Lickey Hills, which consist, in great part, of triassic strata.* 



The Valley of Woolhope, which lies to the west of the 

 southern extremity of the Malverns, about three or four 

 miles from Hereford, is a remarkable instance of what 

 geologists term a valley of elevation ; being a dome-shaped 

 protrusion of Silurian rocks through the Devonian deposits, 

 of which the surrounding region consists. This elevated 

 mass of strata is of an oval form, being six miles long, 

 and four wide. Within this area, the strata of the three 

 upper Silurian series are thrown up into concentric and 

 conformable masses, each dipping outwards from a com- 

 mon centre, and the whole passing beneath the Old Red- 

 sandstone. The central nucleus consists of quartzose 

 grits belonging to the Caradoc sandstone group. The 

 trenches surrounding the central mass have been produced 

 by the degradation of the more perishable beds, and the 

 denudation of the harder rocks.*|* 



I must not conclude this brief sketch of the o-eolo^ical 

 phenomena of the British Silurian system, without men- 

 tioning that evidences of sub-aerial volcanoes have been 

 discovered by Sir H. De la Beche, in Worcestershire and 

 Pembrokeshire. During the period when the Llandeilo 

 flags and their equivalents were accumulated over the area 

 extending from the Malverns to Pembrokeshire, volcanic 

 vents existed, whence molten matter and ashes were ejected, 

 and became intermingled with the detrital accumulations 

 of the period. The volcanic ashes were mixed up with the 

 gravels and sands that are now in the state of conglo- 

 merates and sandstones, and accumulated in beds that are 

 interstratified with the mud and sand. These igneous 



* Silurian System, p. 493. f Ibid- chap. xxii. p. 428. 



