TKANSACTIONS OF SECTION C. 597 



an interchange of its constituents. There is at present little known to indicate which 

 of the above processes, or whether any of theui, have ])roduced tlie ahove deposits, 

 all attempts to trace their origin having thus far been inconclusive.* 



WEDNESBAT, SEPTEMBER 18. 



The following Report and Papers were read : — 



1. Second Report on the Higher Eocene Beds of the Isle of Wight. 



See Reports, p. 89. 



2, A word or two ahont the so-called Concretionary Structures in the 

 Magnesian Limestone of Durham. By Professor A. H. Green, M.A., 

 F.B.S. 



Parts of the magnesian limestone shown in the coast section north of Sunderland 

 are largely made up of masses that assume various strange and fantastic shapes. 

 It was suggested that these were originally tui'aceous deposits, and that their form 

 was in part due to irregular precipitation. In some cases subsequent molecular 

 reaiTangement had set up radiated and other crystalline structures in them. 



3. The Work of the Geological Survey in Northwnherland and Durham. 

 By W. ToPLEY, F.B.S., F.G.S. 



(^Communicated hy permission of the Director-General.') 



The Geological Survej' of Northumberland and Durham was commenced in 1864 

 (the year after the last meeting of the Association in Newcastle) by Mr. Howell, who 

 superintended the work until its completion. The following officers of the Survey 

 have, at various times, assisted in mapping the district : Messrs. Barrow, Bums, 

 Cameron, Clough, Goodchild, Gunn, Lebour, Miller, and Topley. 



The mapping has all been done on the 6-inch scale. Some of the 6-inch 

 maps are published, others are deposited for reference in the Survey Office, 

 London. All is reduced to the I-inch scale. Of these maps two series are issued, 

 one showing the glacial and other euperticial deposits — ' Drift Maps ; ' the other 

 showing the rocks beneath the glacial deposits — ' Solid Maps.' There are also 

 ' Horizontal Sections ' on the scale of 6 inches to a mile, ' Vertical Sections ' on 

 the scale of 40 feet to I inch ; and Memoirs explanatory of the various I-inch 

 maps. An Index-map, on the scale of 4 miles to 1 inch, is in preparation. 



Silurian rocks are exposed in the higher valleys of the Rede and Coquet, and a 

 small faulted inlier, hitherto unknown, has been discovered near Ingram. Few 

 fossils have been found on the English side of the Border, but they are more 

 numerous on the Scottish side, and lix the age of the beds as VVenlock. 



A small but important inlier of Silurian rocks was discovered by Messrs. Gunn 

 and Clough in Teesdale, above the High Force. These beds belong to the Stockdale 

 Shales ; they are traversed by dykes of mica-trap. On the Yorkshire side of the 

 Tees, near the same place, beds belonging to the Volcanic Series of the Lake 

 District have been discovered. 



The Cheviot area has yielded some interesting results. The general structure 

 of this region, and the age of its rocks, were known to Mr. Tate, and the Geological 

 Survey of Scotland worked out the details on the Scottish side before the English 

 Survey had touched the English side. Indeed, the best general descnption of the 

 district is that contributed to ' Good "Words' by Professor James Geikie in 1876. 



' The papers on which the above communication has been founded, have been pub- 

 lished in extenso in the Proc. Boijal Soc. vol. xlvi. pp. 363-369. 



