232 



THE WREKIN. 



Trap Rocks of the Wrekin, Lilleshall Hill, fyc. 



Rocks of trappsean or igneous origin intersect the strata at numerous points on the 

 left bank of the Severn. In Maughmond Hill they cut through the Cambrian System; 

 in the Wrekin and its dependencies, the lower edges of the Silurian System ; in the 

 districts of Little Wenlock, Ketley, &c, the coal-field; and at Lilleshall, both the Silurian 

 rocks and the carboniferous limestone. Of the trap of Coalbrook Dale we have already 

 spoken (p. 109.), and of that of Haughmond Hill we shall hereafter treat in connexion 

 with the Cambrian deposits. Let us in the meantime review the group of the Wrekin. 

 (PL 1 . fig. 11.) This elliptical hill, rising into a narrow crest, is about one mile and a 

 quarter long, and its culminating point is 1330 feet above the sea. In Ercal Wood, 

 the north-eastern prolongation of the axis of the Wrekin, are other rocky masses of 

 similar composition, the highest point of which is seven hundred feet above the sea. 

 They extend in a broken and rugged outline upwards of a mile towards the north-east, 

 and terminate near the high road from Wellington to Shrewsbury. They are separated 

 from the Wrekin by a narrow gorge, and on their south-eastern flank rises a separate 

 hill of about equal height, called Madox Hill, the axis of which is parallel to the 

 Ercal and the Wrekin. Beyond the south-western extremity of the Wrekin, and sepa- 

 rated from it also by a depression, is a conical knoll, called Primrose Hill. (See left side 

 of the wood-cut.) Designating all these hills under the name of the Wrekin, they may 

 be described as essentially composed of rocks of igneous origin, having upon their flanks 

 various strata of the Silurian System, which, in contact with the trap, have undergone 

 (as at the Caradoc) great changes in mineral character. 



The rock most unequivocally of igneous origin, is a pink, deep red syenite, consisting principally 

 of compact felspar, with some white quartz, a few crystals of common felspar, and occasionally dis- 

 seminated chlorite. In the Ercal ridge the chlorite prevails, so as to give the rock a green aspect, 

 small crystals of iron pyrites being also present. In the extensive road-stone quarries, near the 

 Hay Gate, at the northern termination of the hill, are several varieties of compact, pink, and purple 

 felspar, some of which are finely concretionary, with passages into a fine granular structure ; others 

 consist of a very hard compact mass, which in fracture bears a quartzose character, the corneen ? 

 of French mineralogists. In Madox Hill is a fine-grained, pink syenite, and also a rock made up 

 of felspar and green earth, with some veins of carbonate of lime. The summit and centre of the 



