SILUKIA. 
[Chap. II. 
from Linley to Church Pulverbatch, 
the highest of them dipping conform- 
ably under the remarkable quartzose 
ridge of the Stiper Stones. With 
these quartzites and their under- 
lying schists commence the Lower 
Silurian strata as originally denned. 
-§ It is to this huge accumulation of 
| schists, sandstone, grits, and pebbly 
■§, . beds, lying between the valley of 
§ g Stretton and the Stiper Stones, that 
°3 
% .2 the term of < Unfossiliferous Grau- 
8*1 
wacke' was first applied by me in 
_ m 1833, and which was afterwards 
IS 12 Is changed into that of ' Cambrian'*. 
It is important here to remark that 
'•I 1 ft I* the thickness of these rocks in Shrop- 
shire has been estimated, by the 
. «^ «" Government Surveyors, at not less 
than 26,000 feet, as exposed in their 
highly inclined edges, the beds dip- 
ping, at the average inclination of 
about sixty degrees, to the WJNJW.f 
The opposite diagram, reduced 
from my original sections, repre- 
senting the general relations of these 
jj Longmynd or Cambrian rocks to the 
g 3 strata which were first defined as the 
^ Lower Silurian types, will convey a 
* See Proceedings G-eol. Soc. vol. i. p. 475. In 
m this publication of the year 1833, after describing, 
co m a * n descending order, the Ludlow and Wenlock 
r**! iJ4 . O _S rocks as being underlain by ' Shelly Sandstones ' 
1-1 O o o and ' Black Trilobite Flagstones' (the whole united 
jj Sp^ ^3 in 1835 under the term ' Silurian '), I thus spoke 
o o& °f tne subjacent 'Bed Conglomerate, Sandstone, 
E> r^2 r=3 " r§ and Slaty Schist,' forming the higher portion of 
r§ r§ ^ § the Longmynd : — " This is a vast deposit of several 
^ O Pi S S thousand feet in thickness, consisting of very 
rrl of^BP coarse quartzose conglomerates, which alternate 
1-1 H with some schistose beds and much purple- 
jjq ^ £ o> coloured sandstone (the Compound Sandstone of 
£-< £ b3 2 Townsend), the strata of which in Haughmond, 
o 3 <a Pulverbatch, and Linley Hills, Shropshire, are 
P l~ ' 0*W highly inclined or vertical, in conformity with 
M » * .o* *" «" those of the preceding formation. No organic 
NiM^* remains have been observed, by which, and by its 
H very peculiar mineral structure, this formation is 
shown to be entirely distinct from the preceding 
£ (overlying) groups." See also Bhilosophical Ma- 
gazine and Annals of Bhilosophy, 1835, vol. xviii. 
° p. 46; and Silurian System, p. 268, and pi. 32. 
iigs. 1, 2, 3. 
M t According to the same authorities, the Cam- 
brian rocks at Harlech in N.Wales, which are equi- 
valents of the upper portion, are about 8000 feet 
thick. 
