ISopal Itt!3tittttion of (ffireat mritain. 



WEEKLY EVENING MEETING, 



Friday, April 24. 



Sir Benjamin C. Brodie, Bart., M.D. D.CL. F.R.S. Vice- 

 President, in the Chair. 



Professor A. C. Ramsay, F.R.S. 



On certain peculiarities of Climate during part of the 

 Permian Epoch. 



The subject was divided into two parts : 1st, The early geological 

 history of the Longmynd and the. neighbouring Lower Silurian 

 rocks, between the Stiper Stones and Chirbury in Shropshire ; 

 and 2nd, The nature and glacial origin of the brecciated conglom- 

 erates of Worcestershire and part of South Staffordshire, that lie 

 near the base of the Permian strata. 



The Longmynd consists of a high tract of barren ground in 

 Shropshire, formed of the Cambrian grits, conglomerates, and slates 

 that lie beneath the Lower Silurian strata. They attain a height 

 of about 1700 feet above the sea. The beds stand nearly on end, 

 and measured across the strike appear to be about 14,000 feet thick. 

 This appearance may, however, be deceptive, as it is possible they 

 may be doubled over in large contortions, the tops of the curves 

 having been removed by denudation. They have heretofore yielded 

 no fossils except a doubtful trilobite, and the marks of annelides 

 and fucoids. They are overlaid by an equal amount of Lower 

 Silurian strata between the Stiper Stones and Chirbury.* These 

 consist of Lingula flags, and Llandeilo slates and grits full of the 

 ordinary fossils of the period, and are associated with bosses of 

 eruptive greenstone and beds of felspathic trap and ashes. The 

 slates have often a peculiar porcelanic and ribboned character 

 imparted to them by the igneous rocks, and all the igneous phae- 

 nomena of the district are of Lower Silurian date. 



Certain strata, known as the Pentamerus beds or Upper 

 Llandovery and May Hill sandstones, lie at the base of the Wen- 

 lock shale, quite unconformably on the Cambrian and Lower Silurian 



♦ First described in the Silurian System. — Murchison. 

 Vol. II.— (No. 26.) 2 g 



