SEDGWICK ON THE MAY HILL SANDSTONE.
219
detain the reader one moment in a general description of these well-
known sections ; and the accompanying sketch is simply used to help
the memory, and to give coherence to the subjoined remarks.
Fig. 3. — Diagram showing the succession of rocks from the May Hill
Sandstone upwards.
S.W. May Hill. N.E.
1. Coal-iield of the Forest of Dean.
2. Mountain limestone.
3. Old Red Sandstone.
4. Upper Ludlow.
5. Aymestry limestone.
6. Lower Ludlow.
7. Wenlock limestone.
8. Wenlock shale.
g. Woolhope limestone.
10. May Hill sandstone.
The "Woolhope sections are the most perfect and symmetrical ;
but the May Hill section was best for our purpose ; viz. to examine,
and connect together, the two groups which are at the base of the
section. In the May Hill section we have the following groups in
true descending order : — 1 . The Carboniferous series ; 2. The Old-
red-sandstone ; 3. The Ludlow series (Nos. 4, 5, 6 of the sketch) ;
4. The Wenlock series (Nos. 7, 8 of the sketch). Respecting these
four groups there has been no doubt since the Silurian Sections were
first published by Sir R. I. Murchison. 5. These groups are fol-
lowed by thin bands of concretionary limestone (No. 9 of the sketch),
separating the base of the Wenlock shales from the underlying grits
of May Hill. 6. The shelly sandstones and grits which form the
dome-like elevation of May Hill (No. 10).
The last two groups of this section were considered, in the " Silu-
rian System," as Caradoc sandstone. Subsequent labourers, espe-
cially Professor Phillips, have pointed out good reasons for regarding
the bands of concretionary limestone as an integral part of the Wenlock
series ; but he and the other Government Surveyors have coloured and
described the May Hill grits, &c. as Caradoc sandstone.
The bands of limestone last mentioned might, I think, be most
conveniently called Lower Wenlock limestone ; but the name Wool-
hope limestone having for some time passed current, I will here
adopt it. All the Silurian limestones are local phsenomena ; none
of them are so persistent as to offer good terms of comparison be-
tween countries, of the same age, which are widely separated. This
remark applies with all its force to the Woolhope limestone. Round
May Hill it is in many places so degenerate as to have been over-
looked in the sections. At Littlehope (and in other places within
the Woolhope elevation) it is more clearly developed, and cannot
escape notice, as it is extensively burnt for lime. At Presteign it
reaches its maximum of development ; and it there so entirely re-
sembles the most complete form of Wenlock limestone, that for many
years it was confounded with that rock * .

• See Quart. Journ. Geol. Soc. vol. vi. p. 435.