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REFOIIT — 1884. 



It must, liowevcv, bo noted that clsowlicro, as in this district, \vc find 

 intcrvoniii<if bi.'twocii these two series, eitliev an interval of granitoid rook, 

 its in Olen IjDgan, or a fault cutting out a part of the supposed lower 

 Mvies, as at tlie mouth of Glen Torridon. 



Tliis granitoid rock (variously called syenite, diorite, granulite, &c.) 

 was by both the principal disputants, Murchison (with Geikie) and 

 TS'icl:()l, as at lii'st by I licks, considered to bo an intrusive igneous rock. 

 to which th(! obscuration of ilio succession was inainly due. After a visit 

 ■'•i 187!> (o the lioeh ^larce neighbourhood 1 pointed out that there were 

 none of the nsiiiil indio itions of tlie intrusion of a granitic rork, I)ut every 

 indication of a faulted junction, and thiit litholngically the Logan rock 

 (as it hi's been called for purposes of reference) is inseparable from 

 tlio older part of t,ho llebridean series, aud oft(>n e.Khibits indications of 

 intense ernshiiig.' Tliis view is supported by specimens from Assyn! 

 collected by Dr. Callaway, and from Eriboll, by Professor Lapwortli and 

 others; it is maintained by thorn, and is now accepted by Ur. Hicks, '-' 

 We have then to deal with the fact that between the eastern gneiss and 

 the (luartzite-limestone group there is often an irregular wedge of tlie 

 old llebridean floor, bounded on the one side by a fault whose throw is 

 equal to the whole series from the base of the Ttn-ridon sandstot.e 

 upwards (all the Cambrian and Ordovieiiin), and (jn the other (according 

 to the Murchisonian hypothesis) by one somewhat greater. It has been 

 shown by Dr. Callaway and Profi'ssor Lapworth that a prolonged study 

 of the ii.ssumed sequence of the limestone or quartzite and the eastern 

 irneiss in tlieDarness and the Eriboll rerjions briuQ-s to li<'ht most serions 

 stratigraphical difticulties, and that the apparent conformities (where 

 they exist) are better exfilained by an overfold or overtlirust in iiiuiting.'' 



Further, all would admit that the great mass of the central High- 

 lands, wherever it has been studied (excluding some in-folded masses of 

 grit, quartzite, schistose and nlaty beds, very probably Pahcozoie), con- 

 sists of schists and giunsses corresponding very closely with those 

 typified by the rocks in the above-described section from Glen Logan 

 southwards, especially by the moi'o highly altered or more soutliorn 

 members of it. Now, dealing for a moment simply with the lithological 

 aspect of till! question, it has been shown by T)r. Hicks'* (and his view 

 is confirmed by Mr. 1\ Davie?, and accords with my own studies of Ins 

 specimens) that rocks in the main agreeing with the upper portion of 

 the admitted llebridean scries predominate over a broad strip extendinu- 

 in a NNE. direction from Loch Sliiel and the head of Locli Eil; tlmt 

 on the south of this region, about the lower part of Loch Eil and the 

 southern part of the CyJiledonian Canal, rocks bearing a general resem- 

 blance to those of Hen Fyn,near Achnasheen, occur, and on the north oi 

 it a district occupied by similar rocks extends inward from the western 

 r'oasb about Arisaig to the north shore of Loch Carron ; this, crossiiiir 

 the valley leading down to the sea so as to include Ben Fyn and the hills on 

 the north side, stretches northward to include the head of Glen Logan 

 and the region of Loch Pannich ; and, further, that similar rocks oecnr 

 at Gairloch, flanked on the eastern side by the Upper llebridean, wiiich 



' (,). J. G. S., vol. xxxvi. p. 02. Nearly the sunn- view liad indcpontlentlj- occunxd 

 to Ml-. Iludli'ston, J'roc. Gcol. Aft.sur., vul. vi. p. 7.">. 

 - Q. J. (}. .S'„ vol. xxxix. p. 1 4:i. 



^ (). J. (1. S., vol. x.Kxix. p. ;!.""i : GcnJ. .Ifa;/., IV'r. ii.. vol. \, 

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