THE OLDEST MOUNTAIN IN ENGLAND. 
23 
South Shropshire, are good instances of the remnants of these 
eruptions. Immediately to the south-east of the Wrekin, and 
forming a parallel ridge, is a great layer of dolerite, which had 
been intruded amongst the Lower Carboniferous rocks, and 
exposed by subsequent denudation. This mass has by some 
writers been lumped together with the ancient felspathic rocks 
of the Wrekin ; but there is no reasonable doubt that it belongs 
Fig. 3. 
Scale about 8 inches to 1 mile. 
THE WREKIX — ADVANCED STAGE. 
Fig. 3 represents the Wrekin in its "present form. The wedge has been 
further uplifted, tilting up on its flanks the beds of Pre- Cambrian sandstone 
(now quartzite). On the south-east side are also seen two sub-formations of 
Cambrian rock. In early Silurian times, the general relations of the several 
groups must have been as here represented ; though the volcanic nucleus was 
doubtless buried under masses of Cambrian strata. The superincumbent 
envelope must have been removed, and the volcanic wedge exposed to the 
light of day, before the Silurian period had reached its meridian. 
1. Bedded Pre- Cambrian volcanic tuff, dipping north. 
2. Quartzite. 
3. Hollybush Sandstone. 
4. Shineton Shales (Tremadoc). 
to the same eruptive period as the Rowley and Clee Hills. The 
disruptive boss and dykes previously described as occurring at 
the north-east end of the Wrekin, are probably of the same 
epoch. The boss may, indeed, be the consolidated remains of 
the molten rock which filled a pipe or neck, and which sub- 
sequently intruded itself between the adjacent Carboniferous 
strata, though the two masses are now isolated by the denudation 
of the intervening valley. 
In the period of the New Red Sandstone (Permian and Trias) 
the depression was continued, and the Wrekin was more or less 
buried under deposits of red sandstone, accumulated, in all pro- 
bability, in inland seas or lakes. These sandstones may sub- 
sequently have been covered in by the marine strata of the 
Jurassic and Cretaceous epochs, 
