ON TII« AR( II i;.\N KOCK.S OF GltKAT IIKITAIN. 



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extends to tliH slioi'c of Loch Marec, and on the western by similar rocks, 

 but bounded on the northern and southern by the Pala)ozoic grits and 

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

 s(!oms to mo indubitable that the lithological evidence is in favour of Dr. 

 llicks's majjpinjf ; and Mr. T. Davios, whoso opinion is of the greatest 

 weight, is very clear in asserting that the more foliated beds of Gair!och 

 (accepted by Dr. Oeikio, 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 (liinnenthal, 

 Val Piora, etc.), and of Avhich we may take the well-known schists of the 

 Val Trcmola (south side of the St. (Jothard Pass) and of the Val Piora a.s 

 types. Those are likened by Dr. Stcrry Hunt to the Montalban series 

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

 difliculties 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 AIjjs which have been so 

 successfully unfolded by Heim, ]}altzer, and others. 



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

 lands, and of that forming the same part of tlie central Highlands, avouM 

 bo that tlrj Archasau series consists (in ascending order) of («) coarse 

 gneisses (called by Dr. Uicks the Loch Maree series) ; (h) more variable 

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

 quartz-scbists, friable gneisses (Gairloch and Ben Fyn series of the .sanm) ; 

 and (tZ) the very ilaggy series of schists (the Glen Docherty series ot tlie 

 same). The last, in iiis view, may possibly be a series of ro.manie beds 

 of Paleozoic ago overlying the limestone, but 1 incline to consider it 

 (thimgli at present I will lujt venture to speak positively) as representing 

 a yet newer Archaean group — as in the case of the schistes liinirces of the 

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

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

 of the newer u^jon 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 arc regarded as having been thrown 

 into great I'olds (with a general NW. to HE. strike) by earth-movements 

 prior to the Cambrian times ; the crowns of th(; dome-liko masses were 

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

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

 tion eanie an epoch of mountiiin-making, the direction of ])re.s.surc being 

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

 older beds were ftdded togetiier, and inversions or faults with overthrn.st 

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

 eharacters this Hebi'ideau series presents resemblances to the rocks in the 

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

 sliire, and is very like (so I'ar as I know them from s])ecimens) 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 

 fin whieh, however, the felspar is usually whitish instead of pinkish, i)nt 

 thodiil'trence, conspicuous to the eye, is of little real moment) ; in fact, tho 

 litliiilogical and petrological characters of these Hebridean gneisses are 



