14 
SILTTRIA. 
[Chap. I. 
the Cambrian and Lower Silurian rocks of the Highlands range, as before 
said, from N.E. to S.W., the Laurentian, lying beneath them, has a strike 
from N.W. to S.E., and is utterly discordant to them, as laid down in 
the maps of Scotland before spoken of. Considering this great break, and 
seeing that the sandstones and conglomerates which next succeeded were 
derived from the subjacent gneiss after it had passed into a crystalline 
condition, we are lost in the endeavour to form an estimate of the incal- 
culable length of time which must have elapsed between the first accumu- 
lation of the Laurentian deposit and its crystallization, and, after that 
change, to account for the great hiatus which separates that rock from the 
younger deposits made out of its fragments. How vast must have been the 
contortion, dislocation, metamorphism, and denudation which intervened in 
that period, concerning which many leaves in the geological register are 
wanting ! In reviewing the natural features of the stratified succession in 
the Western Highlands, I am therefore led to believe that the lowest gneiss 
of that region is the representative of the Lower Laurentian of Canada — 
the oldest sedimentary deposit as yet known in the crust of the globe. 
In the succeeding Cambrian rocks, traces of animals superior in grade to 
the Eozoon will presently be described ; and those rocks I still consider to 
be the basement- strata of all the deposits of England and Wales. Eor, not- 
withstanding the ingenious and able sketch of Dr. Holl *, who has inferred 
that the crystalline nucleus of the Malvern Hills is of Laurentian age, I 
cannot subscribe to his view, whether I look to the composition and 
direction of these rocks, or to the geological sequence which is there ex- 
posed. The fine-grained, fissile, and foliated Malvern rocks, in which 
felspar and mica abound, do not at all resemble the hard, thick-bedded, 
massive, older gneiss of the Highlands, except in the presence of some 
hornblende. Then, again, these Malvern rocks are parallel to the flank- 
ing Silurian deposits — thus differing in the most marked manner from the 
discordant relations of the Highland rocks, but agreeing exactly with the 
parallelism of the Cambrian to the Silurian rocks in Shropshire, Wales, 
and Scotland. Again, among the miniature series of stratified deposits 
which overlie the crystalline nucleus of the Malverns, there exists no re- 
presentative whatever of those enormously thick deposits of the Longmynd, 
or Cambrian of the Geological Survey. The observer proceeds at once 
from crystalline rocks to the Holybush Sandstone, which was long ago 
shown to be the base of the Silurian deposits of the tract, by Professor 
Phillips and myself. My inference therefore is, that the crystalline schists 
and gneissic rocks of the Malverns represent the older portion of the Long- 
mynd or Cambrian rocks, and that they stand in the place of similar 
rocks in Carnarvon and Anglesey, which are simply the metamorphosed 
Cambrian rocks of the adjacent parts of Worth Wales f . 
* Quart. Journ. G-eol. Soc. vol. xxi. p. 72 &c. Wales,' Memoirs of the Geological Survey, vol. 
t For these conversions of Cambrian strata into iii. pp. 164, 166, 167, 169, 177. See a fuller sketch 
crystalline rocks, see Ramsay's ' Geology of North of the Malvern Hills in Chap. V. 
