V Ol. 60.] OF THE EAST-CENTRAL HIGHLANDS. 437 



low dip characteristic of the Moine Gneisses in this area. Close to, 

 or in contact with it, is the more micaceous portion of the Hone- 

 stones, which are here thicker and so markedly crystalline that it is 

 questionable whether the}* are to be called Honestones or Moine 

 Gneisses. They contain much biotite, and the characteristic original 

 films of chloritic material now largely altered to biotite. These 

 obviously represent the softer, or more micaceous portion of the 

 typical Honestones that are farthest from the margin of the Quartzite. 

 The portion closer to the Quartzite forms the lower hill above the 

 road and is a highly-quartzose, more or less banded gneiss. The flat 

 ground at the foot of the scar between the two types of rock is 

 unfortunately obscured by Drift, and their relation to one another is 

 not at first clear. Briefly put, the doubtful Honestone3, or softer 

 bands, are a little way within the belt of increasing crystallization, 

 but not sufficiently far to give them a decisive character ; the more 

 quartzose gneisses farther down the hill are well within the belt, 

 and their character is unmistakable. 



At this locality, the Pink Felspathic material of the Gilbert's- 

 Bridge area is again intimately associated with the Limestone and, 

 to a smaller extent, with the adjacent rocks ; the most important 

 constituent of this pink material is again microcline. Further, the 

 softer rocks close to the Limestone are identical with the more 

 crystalline portions of the Honestones below Pool Tarf in the Tilt, 

 where, as previously stated, the further passage to Moine Gneiss is 

 practically unbroken. 



We may conclude this account of the mode of ending-off of the 

 Moine Gneisses with a brief description of three sections, in all of 

 which the horizon of the Parallel-Banded material can be fixed just 

 before it becomes too thin to be shown on a map. 



The first occurs about the hill of Creag-na-Dala Bige, in the 

 Invercauld Forest, overlooking the head of the Cairn. To the west 

 of this hill the Moine Gneisses cover a considerable area, although 

 this is largely composed of a single folded band, characterized by 

 pink edges and containing much epidote, already referred to. The 

 gneiss is succeeded to the east by a considerable mass of well-foliated 

 Dark Schist, here highly crystalline and containing some sillimanite, 

 and so much cordierite as to show that it was highly chloritic 

 originally, and is the lower part of the bed (8435). A few small 

 infolds of the Main Limestone occur within this Dark Schist. On the 

 opposite or eastern side of the Dark Schist, the Moine Gneisses are 

 represented by a small thickness of faintly-banded quartzose rock, 

 quite inseparable from the main Quartzite seen a little farther down 

 the hill. 



The second occurs on the hill above Balloch, about a mile and a half 

 east-north-east of Invercauld House, and has been already referred 

 to (p. 414). The thin, faintly-banded, highly-quartzose represen- 

 tative of the Moine Gneisses is here succeeded directly by the Main 

 Limestone (9825) ; and there is clearly a slightly-larger hiatus than 

 at the locality just mentioned. A little farther west, the Parallel- 



Q. J. G. S. No. 240. 2h 



