24 
POPULAR SCIENCE REVIEW. 
In some period succeeding the Trias, certainly later than the 
Lias, probably at the close of the Mesozoic, great dislocations took 
place in a north-east and south-west direction. In very early 
times lines of fracture had been established at the base of the 
Wrekin on each side. Between two of these faults the Wrekin 
had originally been thrust up as a solid wedge of the earth’s 
crust. The disturbing forces had, during successive epochs, in 
the manner described, been acting along these lines of weakness. 
The wedge had been alternately uplifted and depressed, and, in 
some cases, large areas surrounding the lines of more violent 
movement had, to a greater or less degree, shared in the motion. 
These movements were renewed, with great violence, at the close 
of the Mesozoic epoch. Triassic sandstones, as the result of these 
dislocations, now lie faulted against the base of the Wrekin, just 
as they lie along the eastern flank of the Malvern Hills ; and, 
farther to the south-west, Triassic, Permian, and Carboniferous 
strata are in succession thrown down against Cambrian and 
Silurian rocks. 
During successive Tertiary ages, the Wrekin was gradually 
disincumbered of its enclosing Mesozoic envelope by the united 
action of marine and sub-aerial denudation. 
In the Glacial epoch, the mountain again suffered submer- 
gence, partial or entire. Marine sands, containing boreal shells, 
are found on its lower slopes, and testify to the presence of the 
ocean. Subsequently to the formation of these deposits, ice- 
bergs from the north, laden with boulders of granite and felsite, 
were stranded against the flanks of the mountain, and deposited 
their rocky burdens. It is also probable that the Wrekin was 
wholly or in part buried beneath continental ice during some 
part of this period. 
Last of all the sea retired, and the Wrekin made its final 
emergence from the waves. No material change has since then 
taken place ; but the atmospheric forces have been and are still 
at work. Frost, with its million wedges in every square foot of 
exposed surface, reduces the hardest felstone to powder. Carbonic 
acid, dissolved in rain-water, penetrates the felspathic rock, dis- 
solves out the alkaline ingredients, and produces gradual decay. 
Finally, the falling rain washes down the particles loosened by 
frost or softened by decomposition, and the streams that drain 
the mountain deposit them on the lower ground, or carry them 
into the Severn. Thus this “ JEonian hill,” composed as it is 
of hard and intractable mineral matter, is being imperceptibly 
but inevitably reduced to powder, is “ drawn down ” by streams, 
and 66 sown ” as 
“ The dust of continents to he.” 
