Reports & Proceedings — Edinburgh Geological Society'. 141 



than 400 feet above sea-level. This type has once covered the 

 greater part of the Thames Valley that is now at or below this level. 

 As they rise to a greater height the Tertiary pebbles (and flints if 

 present) increase in size. 



Outliers of the finer deposits have recently been met with near 

 Chorley Wood, and on both sides of the Misbourne a little above 

 Chalfont St. Giles. The steady increase in the proportion of small 

 quartz pebbles in this area suggests that they must have entered the 

 district by the Wendover gap, at the head of the Misbourne valley ; 

 this has been proved to be the case. 



The coarser gravels of this composition occur on the south side of 

 the Thames, at varying heights, up to above 600 feet; these all rest 

 on the Chalk. The author has pointed out that there must be 

 corresponding coarser gravels also resting upon the Chalk on the 

 north side of the Thames, and the occurrence described by Mr. Gilbert 

 now shows that this is the case. 



The higher gravels on the south side of the Thames seem to be 

 allied to the Lenham Beds, and this greater age is supported by the 

 considerable denudation that has taken place since this series of 

 gravels was deposited. The post-Glacial denudation of the area about 

 London, away from the immediate neighbourhood of the Thames 

 itself, is quite small in comparison with it. 



II. — Edinburgh Geological Society. 



December 18. — Dr. M'Lintock, Vice-President, in the Chair. 

 (Received January 18, 1919.) 



1. "Lead and Zinc Mining in Scotland," or "Some Scottish 

 Mineral Veins ". By G. V. Wilson, B.Sc, P.G.S. 



Metalliferous mining is an old Scottish industry of which few 

 early records exist. Gold has been worked in many places, especially 

 the Leadhills district. In considering the source of this gold we 

 may suppose that some auriferous quartz veins were exposed in the 

 district prior to the Glacial Period. By the ordinary process of 

 erosion the gold weathered out of these veins and found its way into 

 the river gravels of the streams. The whole country was then 

 subjected to the action of glacier ice, which removed and mixed the 

 gravels with other materials, and deposited the whole as a boulder- 

 clay and drift over a wide area. Since then the local streams 

 denuded the glacial deposits and concentrated afresh the gold in a 

 new set of river gravels. A number of auriferous quartz boulders, 

 including one found by the writer last summer, have been picked up 

 in the Short Cleuch water. 



Silver has been found and worked native at one or two localities — 

 notably Hilderstone and Alva. 



Copper has been worked in many places — the chief being Sandlodge 

 in Shetland; others are Kilfinnan, Bridge of Allan, Tomnadshan, and 

 Kirkcudbrightshire. 



Nickel, cobalt, and antimony have been worked to a small extent. 

 In connection with nickel a very interesting occurrence is that at 

 Talnotry, near Newton Stewart, where the ore occurs as a magmatic 



