134 
PRE-CAMERIAN VOLCANOES 
BOOK II 
whole series of rocks is of igneous origin, luit has been subsequently 
rendered more or less schistose. 
There is one area where the rocks have escaped metamorphism, and 
where they present some of the well-known features of ancient volcanic 
materials. This tract was first indicated by Dr. H. B. Holl as one occupied 
by “ altered primordial rocks and post-primordial trap.” Its evidently 
igneous materials have been examined and described liy different observers, 
among whom Dr. Callaway has contributed some detailed papers on the 
subject. More recently Professor Green, who had the advantage of sections 
exposed in the excavations for the construction of a reservoir for supply- 
ing water to Great Malvern, came to the conclusion that the rocks 
consist mainly of felsites, having many of the characters of rhyolites. 
lYith these are associated felsitic tuff's, while hands of dolerite, probably 
intrusive, form likewise part of the series. So far as the soinewdiat meagre 
evidence allows an opinion to be formed, there appears to be an alternation 
of felsites, lavas and tuffs placed in a more or less vertical position, striking 
in a northerly direction, and traversed by seveial sheets of intnrsive dolerite. 
No junction has been fmmd between these unfoliated A’olcanic rocks 
and the schists that form the core of the range. Judging merely from 
their present relative condition, one would naturally infer that the volcanic 
rocks must be the younger of the two groups. But, as Professor Green has 
pointed out, it is conceivable that the latter may have locally escaped 
crushing, and yet he of the same age as the felsites and epidiorites of the 
neighbouring Eaggedstone Hill, which liaA^e been in jiart considerably 
affected by mechanical moA’ements.^ 
For our present inquiry it is perhaps sufficient to take note that in the 
lieart of the Malvern Hills there lies a remnant of a volcanic district, prob- 
ably of pre-Cambrian age, the rocks of which had been raised up into a 
A-ertical position so as to form islets or reefs in the sea in which the Upper 
Cambrian strata (Hollyhush Sandstone and Upper Lingula shales) were 
deposited. Until some more precise eAudence is obtained as to the geological 
age of these rocks it may he coiiv'enient to place them provisionally Avith 
the A'olcanic Uriconian series. 
vi. THE GHAKNAVOOD FOEEST VOLCANO 
In the heart of England the great Triassic plain is diversified by the 
uprise through it of the peaks and crests of an old Triassic land-surface, 
Avhich are embraced in the district knoAvn as Charnwood Forest. These 
scattered eminences consist of materials not only immensely older than the 
Trias, hut once doubtless buried under thousands of feet of Palseozoic strata. 
They had been laid hare by denudation and carA^ed into pictm-esque crags 
and pinnacles before the Ncav Eed Sandstone Avas deposited around and 
above them. 
^ Op. cit. j). 7. The metamorplii.sni of the igneous rooks of the Malvern Hills into schists has 
been especially investigated by Dr. Callavay. 
