86 Reports and Proceedings — Geological Society of London. 



I. — Geological Society of London. 



I. — December 2nd, 1903.— Sir Archibald Geikie, D.C.L., D.Sc.^ 

 Sec. R. S., Vice-Pi'esident, in the Chair. The following com- 

 munications were read : — 



1. "Notes on the Garnet-bearing and Associated Rocks of the 

 Borrowdale Volcanic Series." By the late Edward Eaton Walker, 

 Esq., B.A., B.Sc. (Communicated by J. E. Marr, Esq., M.A., F.R.S., 

 F.G.S.) 



The first portion of the paper is occupied with an account of various 

 intrusive rocks. A detailed description of sills and dykes of garnet- 

 bearing rocks in the Langstrath Valley is given ; and similar rocks 

 are described occurring as dykes and sills around the Eskdale granite 

 and the Buttermere granopliyre, and also in the Armboth-Helvellyn 

 area. These rocks vary in degree of acidity. They consistof dial)a^e, 

 porphyrite, and granophyre. Evidence of their characters being 

 dependent upon differentiation accompanied by some absorption is 

 offered. They appear to be related to the Eskdale and Buttermere 

 masses of intrusive rocks. 



The volcanic rocks are next considered. Garnets are found in the 

 Falcon Crag Group, in a group of rocks below the great banded 

 ashes and breccias of the Scawfell Group, and in the rocks of the 

 Scawfell Group itself; but do not seem to occur, except as the result 

 of contact-nietamorphism, in the Eycott Group. The most interesting 

 garnetiferous volcanic rocks are those which occur below the Scawfell 

 ashes and breccias. These rocks often have a streaky structure 

 which exhibits four distinct types : resulting from (a) infiltration 

 along planes of weakness, (6) lamination of ash, (c) flow of igneous 

 material, and (d) dynamic action on included fragments. The rocks 

 are not intrusive, but consist of lavas and ashes, often exhibiting 

 alternating bands of rhyolite and andesite. 



The banded ashes of the Scawfell Group also contain garnets. 



In the Haweswater district there is an intercalation of rocks of the 

 Eycott type with rocks possessing the 'streaky' structure. This 

 intercalation appears to be original, and not the result of subsequent 

 earth-movements. 



The garnets are of the almandine type. Thej^ often have a ring 

 of felspar around them, which, when the intrusive rocks are studied, 

 suggests that the mineral is original ; but similar rings occur around 

 garnets in the ashes, showing that the felspars may be formed in 

 solid rock. In certain ashes of the Haweswater district, the existence 

 of cavities in the garnets suggests a uietamorphic origin for the 

 mineral, but it is difficult to understand how the metamorphism has 

 been produced. 



The paper closes with a description of certain undoubted meta- 

 morphic changes. 



