174 Geological Society : — 



dedolomitization. Comparison is made with the dedolomitized 

 Cambrian limestones of Assynt and Skye described by Dr. Teall 

 and Mr. Harker, from which the Port Shepstone occurrence differs 

 in the localization of the affected areas to reaction-rims around 

 foreign boulders, and in the part played by alumina in the formation 

 of new minerals. 



2. ' Recumbent Folds in the Highland Schists.' By Edward 

 Battersby Bailey, B.A., F.G.S. 



A description is presented of the stratigraphy and structure of a 

 considerable portion of the Inverness-shire and Argyllshire High- 

 lands. The district considered lies south-east of Loch Linnhe, and 

 extends from the River Spean in the north to Loch Creran in the 

 south. 



The following conclusions are arrived at : — 



(1) The schists of the district are disposed in a succession of 

 recumbent folds of enormous amplitude — proved in one case to be 

 more than 12 miles in extent. 



(2) The limbs of these recumbent folds are frequently replaced 

 by fold-faults, or ' slips,'* which have given freedom of development 

 to the folds themselves. 



(3) The slipping referred to is not confined to the lower limbs of 

 recumbent anticlines, and is therefore due to something more than 

 mere overthrusting. It is a complex accommodation-phenomenon, 

 of a type peculiar perhaps to the interior portions of folded 

 mountain-chains. In fact, the cores of some of the recumbent 

 folds have been squeezed forward so that they have virtually 

 reacted as intrusive masses. 



(4) In the growth of these structures many of the earlier formed 

 €ores and slips have suffered extensive secondary corrugation of 

 isoclinal type. 



June 15th.— Prof. W. W. Watts, Sc.D., M.Sc, F.R.S., 



President, in the Chair. 



The following communications were read : — 



1. ' The Natural Classification of Igneous Rocks.' By Dr. Whit- 

 man Cross, F.G.S. 



The author reviews the various systems of classification which 

 have been proposed. He discusses the origin of the difference of 

 composition of igneous rocks due to : (1) Primaeval difference, 

 (2) Magmatic differentiation, (3) Assimilation; and points out 



