370 Geological Society. 



the charge to his direction on the 10th, and sailed for Rio de Janeiro 

 on the 13th. 



Annexed to the paper is a journal of the amount of treasure of va- 

 rious descriptions recovered between the 31st of March, 1831, and 

 the 1 Oth of March, 1832, by His Majesty's sloop Lightning. 



There was then read an extract of the letter of instructions, bearing 

 date the 10th of March, 1832, from Commander Thomas Dickinson, 

 then of His Majesty's ship Lightning, to Commander the Hon. S. F. 

 de Roos, then of His Majesty's brig Algerine, on the former re- 

 signing to the latter the charge and direction of the enterprise for the 

 recovery of the public stores and treasures sunk in His Majesty's late 

 frigate Thetis 1 , off Cape Frio. 



The Society then adjourned over the Easter Recess, to meet again 



on the 10th of April. 



GEOLOGICAL SOCIETY. 



Jan. 22. — A paper was read " On the Structure and Classification 

 of the Transition Rocks of Shropshire, Herefordshire and part of 

 Wales, and on the Lines of Disturbance which have affected that 

 Series of Deposits, including the Valley of Elevation of Woolhope," 

 by Roderick Impey Murchison, Esq., F.R.S., F.G.S., &c. 



I. Another summer's work, during which the author revisited 

 Shropshire and the Welsh counties, formerly described, and also 

 examined the eastern side of Herefordshire, with portions of Mon- 

 mouth, Gloucester, Worcester and Staffordshires, has enabled him 

 to lay before the Geological Society much more copious information 

 respecting the " Transition rocks," or " Fossiliferous Grauwacke" 

 of this quarter of Great Britain ; and to subdivide the same into 

 formations. 



The following classification is, therefore, substituted for that pro- 

 posed last vear, being founded upon more extensive observation 

 and an increased knowledge of the organic remains and of the order 

 of superposition. 



1. Ludlow Rocks. — Commencing beneath the old red sandstone, 

 described in the memoir read before the Society, January 8th*, he 

 names the superior formation of the grauwacke series, the " Ludlow 

 rocks." This sandy, argillaceous deposit, has in its centre, the zone 

 of limestone well known at Aymestry, Downton on the Rock and 

 other places, by its containing in abundance the Pentamerus 

 Knightii. It is stated that the black limestone of Sedgeley, near 

 Dudley in Staffordshire, is identical in character and in organic re- 

 mains with that of Aymestry in Herefordshire, and the Yeo edge 

 in Shropshire, and that this calcareous zone is everywhere separated 

 from the Wenlock and Dudley limestone by a thick deposit of shale 

 and flag, to which the author has assigned the name of " Lower 

 Ludlow rock". For the chief characters and order of superposition 

 of the groups of this formation and all those of the descending 

 series, the reader is referred to the annexed tabular view, in antici- 

 pation of details and illustrations which will, at some future time, be 

 laid before the public. The number of unpublished organic remains 

 * See this Journal for March, p. 228. 



