Chap. VII.] 
THE AYMESTEY LIMESTONE. 
129 
■whether I look to the information I derived from his fieldwork or to the 
organic remains with which he liberally supplied me, I have every reason 
to style Mr. Lewis (as I did in the Preface to the first edition) " my most 
efficient coadjutor in all the regions of Siluria." 
The Aymestry limestone is a sub crystalline earthy rock, arranged in 
beds from one to five feet thick, the laminse of deposit being marked by 
layers of Shells and Corals. In the escarpment of the south-western limb 
of the Ludlow promontory, this rock frequently forms bluff cliffs, the in- 
clined strata of which, as seen in the centre of the preceding woodcut, rest 
upon the Lower Ludlow shale, and plunge under the Upper Ludlow rock. 
When cut into, the rock is of indigo or bluish-grey colour, in parts 
mottled by the mixture of white calcareous spar. The quarries, like those 
in all the harder bands of the Ludlow formation, present, as in the above 
diagram, natural backs or divisions, usually coated by a dirty-yellow or 
greenish shale. These are the faces of joints more or less vertical ; and, 
when open, they occasion the rock to separate into rhomboidal masses, which 
are easily detached if the strata are much inclined. The rock is there- 
fore subject to slides or subsidences, particularly where the underlying 
saponaceous ' Walker's ' or 'fuller's earth' prevails. Examples of these 
The Palmer's Cairn Landslip. 
(From Sil. Syst. p. 248. Drawn by the late Eev. W. R Evans.) 
The woodcut exhibits the slope of the beds and the vertical joints, which, in conjunc- 
tion with the lines of bedding, divide the rock into lozenge-shaped blocks. 
slides may be seen at many spots, but at no locality more instructively than 
at the Palmer's Caim or Churn Bank, S.W. of Ludlow, represented in the 
foregoing woodcut. The area there affected exceeds fifty acres. 
This limestone often occupies the summit or capping of the escarpment 
