Reviews —Holl’s Formation of the Malvern Hills. = 317 
partly micaceous, but chiefly hornblendic, with occasional sub-crys- 
talline bands, and beds of coarse-grained diorite interstratified ; tra- 
versed also abundantly by quartzo-felspathic veins, and invaded by 
dykes and masses of erupted trap (diabase): and Dr. Holl has en- 
deavoured to prove that they form a part of the old Pre-Cambrian 
continents, of which the metamorphic rocks of British North America, 
of Scandinavia, Bohemia, Brittany, and the Channel Islands—of the 
Lewis, the Malverns, Charnwood Forest, Donegal, &c., are uncovered 
areas, forming what Professor Dana has called a ‘ Universal Forma- 
tion,’ on which all the other stratified deposits repose. 
The presumed great antiquity of the Malvern metamorphic rocks 
rests upon a variety of evidence. The fact that rocks of Upper Cam- 
brian age rest directly on the flanks of the range shows that the 
erystalline rocks are by position at least as old as the Lower Cambrian 
system. But the author has also shown that the Malvern Range was, 
if not dry land, at least a submarine ridge at the period of the depo- 
sition of these Upper Cambrian beds, by the shallow-water conditions 
they present, and by the fragments of the crystalline rocks of the hills 
they contain ; and that they were laid down on the upturned edges of ~ 
the metamorphic rocks: and further, that from the oblique direction 
of the strike of the metamorphic rocks (NW. and SE.) and from 
other evidence, it is clear that the portion uncovered along the Range 
of the Malverns is only part of a much larger area. The metamor- 
phism of extensive areas, however, can be due only to some general 
' cause. The production of these changes, therefore, in the Malvern 
rocks, their subsequent invasion by granitic veins and trap-dykes, 
and their upheaval and tilting into highly inclined positions, must 
have occupied an enormous period of time, which could not have been 
more recent than the Lower Cambrian epoch; and the period of their 
accumulation (there is a vast thickness of these metamorphic rocks) 
must have preceded this. ‘The conclusion, therefore, appears a fair 
one that these rocks must be of Pre-Cambrian age, and their chemi- 
eal constitution supports this view, inasmuch as, like the rocks of 
Canada, the Hebrides, Scandinavia, Donegal, &c., which are admitted 
to be of Laurentian age, they contain an abundance of basic minerals, 
such as hornblende, epidote, ferro-aluminous mica, &c., and felspars 
oor in silica. 
Dr. Holl then goes on to show the dynamical changes that the range 
has undergone :—first, that it was probably dry land (or at least high 
ground) in the Primordial sea, and that it was subsiding during the 
deposition of the Upper Cambrian series ;—that it was again dry 
land, and had been subjected to denudation, at the period of the de- 
position of the May Hill Sandstone, as shown by the shallow-water 
conditions, and successive overlap of the beds ; and that the subsidence 
which accompanied their deposition was continued through the whole 
of the Upper Silurian period until the close of the Lower Old Red, 
but that elevation then again took place, as seen by the absence of the 
Middle Devonian beds, and by the attenuation, in the direction of the 
Malverns, of the Upper Old Red, the Carboniferous Limestone, and 
Millstone-grit ; the thin deposits of Coal to the North and South of 
