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TRANSACTIONS OF SECTION C. 1027 
2. The Geology of Durness and Eriboll, with special reference to the High- 
land Controversy. By B.N. Pracu, I’.2.S.E., and J. Horne, FERS LE. 
With the permission of the Director General of the Geological Survey, the 
authors gave an outline of the geological structure of the Durness-Eriboll region, 
illustrated by a series of horizontal sections. They showed that the Silurian strata 
of Durness are arranged in the form of a basin bounded on the east side by power- 
ful faults disconnecting them from the same series in Eriboll. The order of 
succession in the two areas is identical from the basal quartzites to the horizon of 
the Eilean Dubh limestone group. On the west side of Loch Eriboll the basal 
quartzites rest unconformably on the Archean gneiss, but on the eastern shore 
there is conclusive evidence of the repetition of various members of the Silurian 
series by a remarkable system of reversed faults culminating in a great dislocation 
which has thrust the Archean gneiss over the truncated edges of the quartzites, 
fucoid beds, serpulite grits, and basal limestone. Reference was made to the effect 
of these mechanical movements on the Silurian rocks and to the development of 
new planes of schistosity in the gneiss above the thrust plane. At intervals, small 
patches of the basal quartzites are met with throughout this mass of Archean 
gneiss, which are abruptly truncated by great reversed faults, but in the district 
between Eriboll and Assynt the whole Silurian succession from the basal breccia 
to the lowest limestone occurs repeatedly above the first great thrust plane, separated 
by wedges of highly sheared gneiss. It was shown that the alteration produced by 
each successive displacement gradually becomes more pronounced as the observer 
passed eastwards across the area. ‘The old north-west strike of the Archaan 
gneiss gave place to a new foliation running more or less parallel with the strike 
of the thrust planes; the felspathic basal quartzites and the ‘ pipe-rock’ pass 
into quartz schists and mica schists, and the Silurian limestone is felted with the 
crushed Archean gneiss. Reference was next made to the outcrop of the great 
thrust plane extending from the Whitten Head Coast far to the south, which 
ushers in a highly schistose series with a N.N.E. and 8.S.W. strike. After de- 
scribing the lithological characters and order of succession of the eastern schists, the 
authors stated that the new planes of foliation had been superinduced by the 
mechanical movements that took place between Lower Silurian and Old Red 
Sandstone time, and that along these new planes a rearrangement and recrystal- 
lisation of mineral constituents took place, resulting in the production of crystalline 
schists. Applying the knowledge thus obtained from the study of the eastern schists 
to the undisturbed Archean masses, they had found conclusive evidence of similar 
mechanical movements in Pre-Cambrian time. ach plane of schistosity exhibits 
the parallel lineation like slickensides trending in the same direction over a vast 
area, while the minerals were oriented along these lines. From a consideration of 
these phenomena the authors inferred that regional metamorphism need not neces- 
sarily be confined to any particular geological period, and further that the planes 
of foliation or schistosity in those areas which had been subjected to regional 
metamorphism were evidently due to enormous mechanical movements which had 
induced molecular changes in crystalline and clastic rocks. 
3. Preliminary Note on some Traverses of the Orystalline District of the 
Central Alps. By Professor T. G. Bonney, D.Sc., LL.D., F.R.S., 
Pres.G.8. 
During the past four years I have made several traverses of the Central Alps 
from north to south, and venture to lay before the Section the general results as 
bearing in some respect on the geology of the Highlands. nok 
1. The ordinary rules of stratigraphy as learnt from most lowland districts 
are commonly quite inapplicable to the Alps. ‘The most highly crystalline and the 
older beds often form the higher parts of a mountain region, the newer the lower, 
The newer beds frequently appear to underlie and dip regularly beneath the older. 
Gigantic folds, overturns, and oyerthrust faults abound, The true stratigraphy of 
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