ON THE ARC1L.EAN HOCKS OF GREAT BRITAIN. 549 



extends to the shore of Loch Maree, and on the western by similar rocks, 

 but bounded on the northern and southern by the Palaeozoic grits and 

 quartzites. I have examined typical specimens from these areas, and it 

 seems to me indubitable that the lithological evidence is in favour of Dr. 

 Hicks's mapping ; and Mr. T. Davies, whose opinion is of the greatest 

 weight, is very clear in asserting that the more foliated beds of Gairloch 

 (accepted by Dr. Geikie, in the passage above quoted, as representing the 

 highest part of the Hebridean series) are lithologically identical with the 

 Ben Fyn series. I may add that this Ben Fyn and Gairloch group has a 

 general resemblance to the more friable gneisses and silvery schists which 

 in the Alps are seen to underlie the zone of well-bedded schists (Binnenthal, 

 Val Piora, &c), and of which we may take the well-known schists of the 

 Val Tremola (south side of the St. Gothard Pass) and of the Val Piora as 

 types. These are likened by Dr. Sterry Hunt to the Montalban series 

 of the American continent. It cannot be denied that the stratigraphical 

 difficulties which are presented by this view of the infraposition of the 

 Eastern Gneiss to the Palaeozoic series are very great, but they are not 

 greater than exist in many sections in the Alps which have been so 

 successfully unfolded by Heim, Baltzer, and others. 



The more modern reading of this district of the north-western High- 

 lands, and of that forming the same part of the central Highlands, would 

 be that ths Archaean series consists (in ascending order) of (a) coarse 

 gneisses (called by Dr. Hicks the Loch Maree series) ; (b) more variable 

 bedded gneisses (the Loch Shiel series of the same) ; (c) mica-schists, 

 quartz-schists, friable gneisses (Gairloch and Ben Fyn series of the same) ; 

 and (d) the very flaggy series of schists (the Glen Docherty series of the 

 same). The last, in his view, may possibly be a series of remanie beds 

 of Palaeozoic age overlying the limestone, but I incline to consider it 

 (though at present I will not venture to speak positively) as representing 

 a yet newer Ai'ckaean group — as in the case of the schistes lustrees of the 

 Alps. How far it is possible to separate these is at present, as iu the 

 Alps, difficult to pronounce, but if there were an unconformity or overlap 

 of the newer upon the older series some of the stratigraphical difficulties 

 would certainly disappear. 



In accordance with this view (so far as the above-mentioned district 

 is concerned), the Archaean rocks are regarded as having been thrown 

 into great folds (with a general NW. to SE. strike) by earth-movements 

 prior to the Cambrian times ; the crowns of the dome-like masses were 

 worn away by denudation, and on these were deposited the Torridon sand- 

 stone and other Palaeozoic rocks. At the end of this period of sedimenta- 

 tion came an epoch of mountain-making, the direction of pressure being 

 from NW. to SE. (roughly, at right angles to the former), and newer and 

 older beds were folded together, and inversions or faults with overthrust 

 were produced on a gigantic scale. We may add that in its general 

 characters this Hebridean series presents resemblances to the rocks in the 

 Malvernian region, and to the granitoid rocks of Anglesey and Carnarvon- 

 shire, and is very like (so far as I know them from specimens) to the 

 Lower Laurentians of North America (including Greenland). It also 

 resembles the coarse gneisses of the Channel Islands, and of several districts 

 in Europe, including the Ur-gneiss, or protogine of the Alpine chain 

 (in which, however, the felspar is usually whitish instead of pinkish, but 

 the difference, conspicuous to the eye, is of little real moment) ; in fact, the 

 lithological and petrological characters of these Hebridean gneisses are 



