Vol. 60.] 3JOINE GNEISSES OF THE EAST-CENTRAL HIGHLANDS. 431 



known at present, this increase is more marked in the lower part of 

 the Schist than in the upper. 



Of all these patches of Dark Schist, the most interesting is that 

 which lies apparently on the top of the Limestone in the river- 

 bank at the first bend below Marble Lodge. (See fig. 5, p. 430.) 

 Here the Limestone is shown resting in an eroded hollow of the 

 attenuated Parallel-Banded Rocks into which the Moine Gneisses 

 have slowly passed, while lying apparently above the Limestone 

 is the patch of Dark Schist now mentioned. It is a dark, somewhat 

 massive rock, evidently rich in biotite, but containing a number 

 of very minute lenticular films of quartz, suggesting that, as 

 we approach an area of more sandy deposition, the Dark Schist 



Fig. 6. — Diagram showing the Dark Schist and Parallel' Banded 

 Rocks apparently on opposite sides of the Limestone, while in 

 reality they are on the same side. 



A B 



" " " •■ •• it ii ii H H n ii M ii •■ » »• 'I ii m ii » " n Ij Lrrvestart^e 



"I »l '• •' » II .. II >i li II »• U '■ H " II -r. r a t . . 



TTTi-*- " ■ " i, " " " ,. " " Jl^^«— ■ in— Dctrk. ScliMst 



ii ii ii 



S cvtud.ecLItoc.ks 



Sh,&wlrvtj lirce, of JCroslon. prior* lo •fbVdJ.ix.q . 



rk. Sc7iLstr 

 LiTLCstorvc 



Vca^aLLe l-B tended R ocfes 



After folding, so that th,a point A lies directly 

 over th,e point B. 



has become more quartzose (10,421). The rock contains much 

 granulitic quartz, which represents the minute lenticles referred to, 

 and a great quantity of more or less aggregated crystals of red 

 biotite ; the typical felspar with much dark dust, like the Glen- 

 Callater hornfels, is abundant, and there is one crystal of andalusite. 

 It is clearly a slightly-siliceous phase of the upper part of the Felspar- 

 Hock. The occurrence of the Felspar-Rock above a thin band of 

 Limestone, with the Parallel-Banded Rocks below it, seems, at first, 

 conclusive evidence that the limestone must be the Little Limestone. 

 In reality it is an ideal example of the kind of deception so often 

 produced by folding of a slightly-vague succession in the Central 

 Highlands. If we consider carefully the meaning of the sporadic 

 occurrence of lenticular patches of Dark Schist below Gilbert's 

 Bridge, it becomes obvious that the folding may so involve one of 



