Geological Soviet)/. 287 



Mining & Mechanical Engineers, contain a large number of 

 borings made in the northern coalfield. A considerable proportion 

 of these are most valuable in showing the nature and distribution 

 of the superficial deposits. From them and from field-mapping it 

 is possible to form a fairly- accurate conception of the pre-Glacial 

 floor of the district and its drainage, and also of the relative 

 changes of level before, during, and after the Glacial Period. The 

 chief superficial deposits include the following : — (1) the stony 

 Boulder-Clay ; (-) the Upper Clay, including (a) the prismatic 

 clay and (6) the leafy clay; and (3) deposits of Sand and Gravel 

 occurring below, in, or upon the Clay. The last include Raised 

 Beaches, which decline in height when traced northward and 

 southward from Cleadon and Fulwell, with a gradient of from 

 3 to 6 feet per mile. 



The surface-deposits lie arranged in the valleys formed before the 

 Glacial Period, and often reach a considerable depth. They fit upon 

 and level up the Glacial inequalities of the country, and are not found 

 above 1000 feet. The base of the Drift is in some cases as much 

 as 140 feet below sea-level, and in one spot the thickness bored 

 through is 233 feet. By inserting all available borings in maps, 

 it is possible to gain some idea of the direction and depth of the 

 valleys. In this way the following pre-Glacial valleys have been 

 located : — The Tyne and its tributaries, corresponding in general 

 trend with the present Tyne, which is superimposed upon it : the 

 • Wash." which joins the present course of the Wear with the Tyne, 

 and has the Team superimposed on its northern part ; the upper 

 Wear, which received all the waters from the west of Durham 

 county, took up several large tributaries between Bishop Auckland 

 and Durham city, and passed through the ' Wash ' into the Tyne ; 

 the Sleekburn Valley ; and the Druridge-Bay depression, into which 

 the pre-Glacial Coquet probably ran. Thus in pre-Glacial times the 

 Tyne and the Tees were the major rivers, and the other streams were 

 tributary to them ; the main changes have taken place in the lower, 

 and not in the higher, parts of the rivers. The post-Glacial Wear 

 has breached the Permian escarpment, and many gorge-like valleys 

 have been cut since the uplift which produced the Raised Beaches. 

 The dependence of the contour of the country on its geological 

 structure was much more pronounced in pre-Glacial times than 

 present. 



December 7th.— J. E. Marr, Sc.D., F.R.S., President, 

 in the Chair. 



The following communication was road : — 



1 The Chemical and Mineralogical Evidence as to the Origin of 

 the Dolomites of Southern Tyrol.' By Prof. Ernest Willington 

 Skeats, D.Sc, F.G.S. 



Ptecent work on modern coral-reefs has shown that these lime- 

 stones contain very little, if any, insoluble residue. The study of 



