TIIK Ai;< IU.AN SO II 



to and beyond Loch Rannoch, as well as to the eastern end of 

 Ijoch Leven, but south of this line it becomes infolded with the 

 ( irumpian Series. 



The whole of this area has now been surveyed by the staff of 

 the Geological Survey of Scotland, and some important conclusions 

 have been reached. These have been cautiously announced from 

 time to time in the annual "Summaries of Progress," from which 

 extracts and abstracts will here be given. 



In 1904 and 1905 it was found that over a large area embracing 

 parts of Ross, Inverness, and Nairn the metamorphosed rocks 

 could be separated into two divisions : (1) a complex group consisting 

 partly of gneisses of Hebridean type and partly of altered sedimentary 

 rocks ; (2) certain gneissic schists of both siliceous and pelitic types 

 which, being intimately connected, were termed the Moine schists. 

 Further, the mapping of these areas showed that the Hebridean 

 gneisses occurred as inliers surrounded by Moine schists, and that 

 the latter appeared to lie unconformably on all the members of 

 group 1 ; the lowest part of the granulitic schists being a band 

 containing fragments of felspathic gneiss and having all the asj>ect 

 of a sheared conglomerate. 



These conclusions have been confirmed by subsequent work, and 

 the altered sediments in the Hebridean complex are found to 

 include crystalline marbles, calcareous silicates, and brown mica- 

 schists which are often graphitic, associated with banded hornbleudic 

 gneisses. The reader will perceive that there is a striking 

 resemblance between this series and that of the Loch Maree Beds 

 above described. Dr. Flett, writing in 1905, says "such rocks are 

 a characteristic part of the Lewisian in certain areas " (t.. Glenelg 

 and Loch Maree) and remarks that they diH't-r widely from any of 

 the Moine Schist Series. It is evident that two sedimentary 

 series are present in the Moine schist area, the one associated with 

 the Hebridean, and of considerable thickness, but largely eroded and 

 removed before the deposition of the other (i.e. the Moino schist*). 



The Moine schists present two different tyj>es of rock which can 

 be separately mapped; these are (1) psammitic schists or flaggy 

 granulites composed of quartz, felspar, and biotite, (2) pelitic <>r 

 argillaceous schists now converted into rnica-schiste in which white 

 muscovite mica predominates. The mapping of Ross and Inverness 

 has led to the belief that these are not merely successive but that 

 there are two bands of psammitic and two of pelitic schists ; tlu-iv 

 are also occasional seams of quartz-schist and of calcareous adust. 

 The whole mass of the Moine schists has apparently been formed 

 out of a series of sandstones and sandy shales. 



Proof of the last statement has recently been obtained by Messrs. 



