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. 

 VOL. IX. — PART I. Q 



