558 
glacial movement, and at localities where such direction was not 
previously known, led to conclusions entirely in harmony with 
those already reached in Pennsylvania and with those held by 
the Irish geologists. One of the best examples falling under the 
former category was among the local glaciers in the mountains 
of the Dingle promontory, a region not invaded by the great 
confluent ice-sheet of central Ireland. The striated beds of 
these small glaciers, beginning in a ‘‘ corey ” and bounded below 
by a semicircular terminal moraine, are beautifully defined and 
afford good opportunities for strize study. It was found that ov 
upward slopes or in flit surfaces the strie as a rule are blunt at 
the end towards which the motion was directed, but that in davn- 
ward slopes the reverse is generally thz case. While this rule does 
not hold good for every individual scratch at a given locality, it 
has been found most useful when applied to striated surfaces in 
general. At Glengariff, where some finely striated surfaces 
occur, a number of tracings were taken directly from the rock, 
which clearly show the broader ends of most of the striz to be 
to the south, the direction towards which the glacial stream 
advanced. Similar observations were made at several localities 
south of the Shannon. Finally, as an instance where the direc- 
tion of glaciation was previously unknown, certain strize were 
described which the author had observed on the top of the cliffs 
facing the Atlantic at Kilkee. These point N. 58° W. and 
S. 58° E., and the question to be determined was whether the 
glaciation proceeded from the Atlantic towards the land or 
whether it went north-westward and out to sea. The form of 
the stricee alone decided it. Their broad blunt ends were as a 
rule toward the north-west, the surface being horizontal, a fact 
which, taken in connection with other observations made about 
the mouth of the Shannon, showed that a great ice stream had 
flowed westward along the valley of the Shannon, and had 
opened out fan-shaped as it plunged into the sea. 
Th? Geolozy of Duvness and Eriboll, with special Reference to 
the Highland Controversy, by B. N. Peach, F.R.S.E., and J. 
Morne, F.R.S.E., Geological Survey of Scotland.—With the 
permission of the Director-General of the Geological Survey, 
the authors gave an outline of the geological structure of ihe 
Durness-Eriboll region, illustrated by a series of horizontal sec- 
tions. They showed that the Silurian strata of Durnes; are 
arranged in the form of a basin, bounded on the east side by 
powerful 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 limestone group. 
On the west side of Loch Eriboll the basal quartzites rest un- 
conformably on the Archzean 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 Archeean 
gueiss over the truncated edges of the quartzites, fucoid beds, 
serpulite grit, and basal limestone. Reference was made to the 
effects of these mechanical movements on the Silurian rocks, 
and to the :developments 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 
Archzean 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 lime- 
stone oceurs 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 
Archean gneis; 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 Archzan gneiss, Reference was next made to the out- 
crop of the great thrust-plane extending from the Whitten Head 
coast far to the south, which ushers in a highly schistose series 
with a north-north-ea t and south-south-west strike. After 
describing the lithological characters and orde« 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 re-arrangement and re- 
crystallisation of mineral constituents took place, resulting in 
the production of crystalline schists. Applying the knowledge 
thus obtained from the study of the eastera schists to the un- 
disturbed Archain masses, they had found conclusive evidence 
NAT ORE 
of similar mechanical movements. Each plane of schistosity 
exhibits the parallel lineation like slickensides trending in the 
same direction oyer 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 
necessarily be confined to any particular 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. 
The Highland Controversy in British Geology : its Causes, Course, 
and Consequences, by Chas. Lapworth, LL.D., F.G.S., Professor of 
Geology and Physiography, Mason College, Birmingham.—The 
author gave a résumé of the views of the earlier geologists respecting 
the geological age and possible mode of formation of the High- 
land metamorphic rocks; and sketched, in brief, the rise and 
progres; of the controversy between Sir Rod. Murchison and his 
followers on the one hand, and Prof. Nicol, of Aberdeen, on 
the other, till its temporary close in 1861, by the publication of 
the Highland Memoir of Murchison and Geikie. He then 
reviewed the reopening of the controversy by Dr. Hicks in 1878, 
and the work of the Archzean geologists, up to the date of publi- 
cation of Dr. C. Callaway’s paper in 1883, in which Nicol’s 
view of the great physical break between the Palzeozoic rocks 
and the Eastern or Upper Gneissic series was shown to be 
correct, but the so-called Eastern gneiss was provisionally 
erected into a new Archzean system, the Caledonian, having the 
Arnaboll gneiss as its lower member. The author next gavea 
summary of his own views as deduced from his personal study of 
the Durness Eriboll district in 1882 and 1883, and published in 
1884, illustrating these by coloured maps and sections. He 
held that (exception being made of the local Torridon Sand- 
stone) the only rock-formations in the Durness-Eriboll area are, 
as Nicol originally contended: (1) The Archean or Hebridean 
gneiss; and (2) The Palozoic quartzites, fucoid beds, and 
limestones, But the so-called upper gneiss or eastern meta- 
morphic gneiss appears to be composed of elements derived 
from one or other of the foregoing There is no conformable 
ascending succession from the Palzeozoic rocks into this Eastern 
Metamorphic series. The line of contact i:, generally speaking, 
a plane of dislocation, and where this is wanting the Paleozoic 
rocks rest unconformably upon one of the members of the 
eastern gneiss. The present physical relations of the eastern 
metamorphic series are the effect of lateral crust creep, by which 
the eastern metamorphic rocks have been forced over the 
Palzeozvic rocks in grand overfaults to the west, often for many 
miles. This Eastern Metamorphic series is conposed of two 
petrological members, the Avnadoll gneiss to the west, and the 
Sutherland schists and gneisses to the east, having between them 
a series of variegated schists possessing characters common to 
both. The Arnaboll gneiss is simply the easterly extension of 
the Hebridean of the west The remainiag gneisses and schists 
of the eastern m2tamorphic series are main!y composed of re- 
metamorphosed Hebridean, with ‘included patches of igneous 
and Palzozoic material. The planes of schistosity which divide 
the layers of the Upper Gneissic series are not planes of bedding, 
but planes of dislocation. The dip and strike of these planes 
have been given to them sinc2 Silurian times by the agency of 
the great earth-movements. In some instances the original 
stractures of the rocks are still recognisable ; usually, however, 
they are wholly obliterated : the old minerals have disappeared 
as such, and new minerals have been developed, The Eastern 
Gneissic series has thus no pretension whatever to the title of a 
sedimentary rock-system. It is a petrological roc’s-massif, a 
metamorphic compound, composed of local elements of very 
different geological ages. In all their essentials these views 
appear to agree with the far more contended and minute results 
worked out independently, and published by Messrs, Peach and 
Horne in November 1884. 
In the second part of his paper the author gave a summary of 
the work accomplished amonz the metamorphic rocks of the 
Alps and Eastern Germany by Heim and Lehmann; and de- 
scribed the several types of rock-metamorphism found in the 
Eriboll district, as worked out by himself The Arnaboll 
(Hebridean gneiss) can be trace 1 stage by stage from spots where 
it retains its original strike and petrological characters, to others 
where it acquires the normal strike and mineralogical features of 
the ordinary Sutherland schists. The old planes of schistosity 
become obliterated, and new ones are developed ; the original 
crystals are crushed and spread out, and new secondary minerals, 
[ Oct. 8, 1885 : 
f 
