THE FRESH- WATER LOCHS OF SCOTLAND. 285 



Still further east, this characteristic zone has been followed from Ben 

 Wyvis across Strath Glass and Strath Rusdale to the hills near Fearn. 



The constant reappearance, throughout the metamorphic area of the 

 Conon basin, of the two main subdivisions of the Moine series suggests 

 the repetition of these zones by folding. Indeed, such is the view 

 adopted by the Geological Survey, and hence the actual thickness of 

 this series may be much more limited than the persistent dip of the 

 strata in one direction would lead us to suppose. The researches of the 

 Survey indicate a probable order of succession in these schists which 

 obtains in the tract between Ben Wyvis and Ben Dearg, and between 

 Garve and the Carron that flows into the Dornoch firth. 



In the flaky muscovite biotite schists, and in the quartzose granulites, 

 bands of garnet amphibolite and hornblende schists occur, which have 

 a wide distribution and are characteristic of certain horizons. 



Reference must now be made to the foliated granite, intrusive in 

 the Moine series, which is one of the most interesting features in the 

 geology of the Conou basin. Its boundaries are of prime importance, 

 because the distribution of the boulders supplies valuable evidence 

 regarding the direction of the ice-flow during the glacial period. There 

 are two important masses of these older intrusive rocks. The larger 

 one extends from Cam nan Aigheinn, near the head of Strath Rannoch, 

 north-east by Carn Chuinneag to Cnoc an Liath-bhaid beyond Strath 

 Rusdale, and measures about 12 miles in length and about 5 miles in 

 breadth. The smaller one stretches from the hills above Loch Luichart 

 north-east by Inchbae to Carn More east of Strath Rannoch, being 

 about 5 miles long and less than 3 miles broad. Again, on the north 

 shore of Loch Luichart there are four outcrops of foliated granite, 

 evidently belonging to the same set of intrusions. The Inchbae type 

 of augen-gneiss or granite is well known, with large porphyritic crystals 

 of orthoclase felspar oriented in a definite direction, enclosed in a 

 granulitic ground-mass of quartz, felspar, and micas, together with 

 crystals of garnet and sphene. This coarse porphyritic variety is 

 largely developed in the Carn Chuinneag mass, where it is associated 

 with foliated riebeckite granite or augeii gneiss. Frequently the rock 

 is fine grained, and merges into a finely crystalline schist. 



Evidence has been obtained that these older granite masses with 

 their basic modifications were intruded into the series of Moine 

 sediments before they were converted into crystalline schists. A well- 

 marked aureole of contact metamorphism accompanied this intrusion, 

 which in places has been obscured by subsequent deformation. But 

 at intervals round the margin the sediments are hornfelsed, and still 

 show their original bedding-planes, while garnets and crystals of 

 andalusite have been developed. It is further apparent that the granite 

 masses and the Moine sediments have been subjected to a common series 

 of dynamic stresses, for the planes of schistosity in the granite are 



