GG 
SILUKIA. 
[Chap. IV. 
Silurian, a thin intermediate zone representing the Llandovery rocks, to 
be described in the sequel, as well as all the Upper Silurian group. 
The flat country in the distance is composed of Carboniferous rocks and 
New fled Sandstone. 
The real order and thickness of the strata exhibited in the sketch, 
however, is best understood by examining this detailed section. 
B/EI&.TIONS OF THE CARADOC FORMATION, SHROPSHIRE. 
N.W. S.E. 
Lawley. Hoar Edge. Chatwell. G-retton. Ape Dale. 
* a b c d d e f 
(From the large Section of the Government Surrey, made by Mr. Aveline.) 
* Igneous rocks, a. Sandy shales, b. Hoar Edge grits, c. Shales, d, d. Shelly 
sandstones, e. Cheney Longville flags. /. Trinucleus shales, h. Llandovery lime- 
stone, i. Wenlock shale. 
The strata which compose the great mass of the formation to which 
the name 'Caradoc Sandstone' was assigned succeed each other in the 
following order. The lowest beds, which are clearly exposed, dipping 
away from the intrusive rock (*), are sandy shales (a), with some courses 
of shelly sandstone, in part a bastard limestone, which rise to the sur- 
face in the hilly grounds of Acton Burnell, and are thence prolonged 
by Frodesley to Lawley, or the terminating hill of the eruptive ridge. 
From that point to the valley (Ape Dale) under Wenlock Edge the suc- 
cession of the strata is clear. The lowest beds, or sandy shales (a), have 
been hollowed out into a valley. The next overlying strata, as seen in 
the sketch and section, consist of light-coloured, yellowish, siliceous sand- 
stones, in part coarse grits (b in the Section), which occupy the sharp 
ridge called the Hoar Edge, along which they are extensively quarried, 
and are seen to plunge at high angles to the south-east. 
Another valley succeeds, which has been excavated in softer and more 
shaly beds (c). These, resting upon the siliceous rocks of the Hoar 
Edge, dip under a second sandstone ridge (d), which extends by Cbat- 
wall and Enchmarsh to Soudley. These last-mentioned sandstones (d) 
contain layers of fossil shells, which occasionally abound so much as to 
convert some of the beds into impure limestones. Their prevailing colour 
is a dirty dull or purplish red ; but they are occasionally variegated with 
brownish, yellowish, and greenish tints. In some quarries not far from 
Acton Scott they are striped in ribbon-fashion with dark-red and light- 
green layers ; and, being here and there also spotted, they thus resemble 
both the Old and New Red Sandstones of long- subsequent eras. Along 
the ridge of Enchmarsh, or at Soudley, they are extensively quarried 
for use, and are as easily worked as many freestones of the younger for- 
mations, reckoning from the Carboniferous sandstones upwards. They are 
