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POPULAR SCIENCE REVIEW. 
doubtless more quickly thrown up, and it is not unlikely grew 
to vaster proportions, than the average of existing volcanic 
mountains, but there is no essential difference in their physical 
and mineral constitution. 
It must not be supposed that the Wrekin represents a volcano 
such as Etna or Vesuvius, or even such dilapidated cones as are 
dotted over the Miocene region of Central France. In the 
Wrekin there is no trace of cone-structure whatever. The 
mountain is bedded like the limestones and shales of Wenlock 
Edge, or the Chalk strata of Sussex. Even in volcanoes of 
Tertiary age, denudation has often left nothing remaining but 
the amorphous roots or foundations of what was once a lofty and 
symmetrical cone ; and in regard to volcanic mountains of an 
epoch to which the Tertiary periods are but as yesterday, we have 
infinitely less reason to expect any traces of the original cone- 
structure. 
The Wrekin is chiefly composed of a great bedded series 
consisting of alternations of felstones (felspathic lavas) and 
felspathic tuffs. At the north-east end are beds of volcanic 
breccia, alternating with fine-grained ashes. Underlying these 
are pink and white felstones, displaying a distinct banded struc- 
ture, due, it is supposed, to the flowing motion of the rock in its 
original form as molten lava. Towards the summit of the moun- 
tain we come again to a hard pink breccia ; and at the summit 
the rock is a compact purple felstone. On the south-west flank 
of the hill is another exposure of tuff. The spur called Primrose 
Hill, the south-west extremity of the range, is composed of a 
brick-red felstone, passing, by the addition of quartz and a little 
mica, into an imperfect granite. 
These lavas and tuffs have a distinct dip to the north, or a 
little to the west of north, at an average angle of about 45°. 
The direction of the ridge being N.E. and S.W., and the strike 
of the beds being about east and west, it will be seen that the 
beds strike across the ridge at an acute angle, so that the 
direction of the range and the shape of the mountain are not 
materially determined, as is commonly the case in mountains 
composed of ordinary stratified rocks, by the strike and dip of the 
beds. A section drawn at right angles across the ridge repre- 
sents the strata with a seeming dip to the north-west at a low 
angle. This will be readily understood when it is remembered 
that such a section would cut the direction of true dip at an 
acute angle. This discordance of the strike of the strata with 
the strike of the range will remind geologists of the structure of 
the Malvern Hills, in which schistose rocks strike north-west 
and south-east across a north and south ridge. 
It has been shown that the volcanic rocks of the Wrekin are 
as clearly stratified as the limestones and shales of Wenlock 
