Prof, C. Lapworth — Close of the Highland Controversy. 105 



we regard these green schists, etc., above the Limestone in the Sango 

 Bay section as (forming part of) a true (sedimentary) sequence, we can 

 prove with equally valuable evidence, indeed upon identical grounds — ■ 



(1) In Sango Bay that these green schists overlie the Limestone. 



(2) In (near) Arnaboll that they follow at once to the basement 

 bed of the Quartzifce. 



(3) In EriboU (in some localities) that they are interstratified with 

 the Hebridean. 



(4) And (in other localities) that they trough the Lower Quartzite, 

 coming out from below it. 



(5) And also, as in Cfaig Faolinn, that they are the junction 

 (transition) beds of the Lower and Upper Gneissic Series. 



In other words, that they are below the Ordovician, above the 

 Ordovician, in the Quartzite, above the Quartzite, in the Hebridean, 

 and in the Upper Gneiss (so called) all at one and the same time ! 



I believe at present that the great area of metamorphic schists 

 of Sutherland and the Central Highlands is, as a whole, neither 

 Archaean nor Ordovician. The Sutherland Gneiss — Arnaboll — is 

 Archfean. The Sutherland Schist has been manufactured ^ since 

 Silurian times. For all I know, there may be large areas (in the 

 Central Highlands, etc.) composed wholly of Archsean (Laurentian) 

 rocks, or of Cambrian or pre-Cambrian rocks. When the meta- 

 morphism of the Highland area began I think that it is impossible 

 to say, and maybe always impossible. One thing seems pretty clear 

 to me — the so-called oldest beds of the Highland succession of the 

 Schistose Series of the N.W. Highlands are the newest in point of 

 time. The zone of intermixture and raetamorphism (in Sutherland) 

 travelled to west from east, and the last beds (schists) manufactured 

 are those now in contact with the Assynt Series in Durness, Eriboll, 

 and Assynt. 



Strikes, dips, and visible sequences are worse than useless in these 

 metamorphic rocks as indices of chronological sequence. I cannot 

 help believing that we have in the Highlands merely the remains 

 of a degraded mountain complex. That fragment of the N.W. 

 Highlands where the fossil-bearing beds occur, is the newest (of its 

 component ranges) in point of time. Some ranges were cei'tainly 

 in existence in the Highlands in the Old Red times, and, for all we 

 know to the contrary, some in Silurian times also. The Highland 

 area has, I consider, been the theatre of mountain-making, and of 

 igneous action again and again, since then. If the same crumpling 

 has taken place over its whole surface as has certainly taken place 

 in Eriboll, its present width must be the merest fraction of its 

 original extent, and the manufacture of its schists and gneisses may 

 have gone on in some localities below its surface from pre-Cambrian 

 times to the present without interruption. 



The attempt to claim all its (Central Highland) rocks as pre- 

 Cambrian is perhaps a little more justifiable than the attempt to 



' [i.e. the heterogeneous materials of which it is composed h.ave underg-one 

 re-arrangement, and have received a new and a common set of potrological 

 features, through the agency of the great Earth-mill). 



