Vol. 55.] AXD FORSTERITE PROM TBTE GLEIfELa LiaiESTOKE. 375 



East of the myloni'/ed rock all the rocks of sedimeutar}" aspect are in 

 a greatly altered condition, and there are none that can be claimed 

 with confidence either as Cambrian or Torridonian. The gneissose 

 and schistose rocks in which the limestones occur closely resemble 

 parts of the Lewisian Gneiss Series of Sutherland and Ross-shire, 

 and we feel little doubt that they belong to this series. This, 

 however, cannot be rigidly proved. 



The rocks next to the limestone are not always of the same kind, but 

 no gneissose or schistose rocks are seen to cross limestone. It seems 

 probable that some of these rocks represent sediments which are of 

 approximately the same age as the limestone, and were altered at 

 the same time as it; but the rocks of this class are intricately 

 intermixed with others which have rather the aspect of gneisses and 

 schists derived from igneous rocks, and in our present state of 

 knowledge it is sometimes extremely difficult to separate the one 

 class from the other. Immediately under one of the limestone- 

 exposures on the north side of the Little Glen of Glenelg, there is 

 a schistose rock (7940) ^ which contains many small flakes of brown 

 mica and specks of pyrites. About ^ mile south-east of the same 

 exposure, there is a garnetiferous biotite-schist which contains many 

 small crystals of kyanite. Both these schists seem indistinguishable 

 in hand-specimens from some of those metamorphosed sediments 

 of the Braemar Highlands to which our attention has been called 

 by our colleagues Mr. G. Barrow and Mr. E. H. Cunningham-Craig. 

 Again, on the hill, nearly | mile slightly south of east of Lochan 

 Cul a' Mhoil (Ross-shire 6-inch map 123), there is a gneissose rock 

 (7908) which Mr. Teall states to be formed essentially of layers of 

 zoisite and microcline, mixed with other darker layers of pyroxene, 

 calcite, and sphene. This rock occurs within 100 yards of a lime- 

 stone, and it is undoubtedly allied in character to rocks found in 

 close association with limestones in Donegal and in the South-eastern 

 Highlands. Besides the above-mentioned rocks there are others, 

 in the gneissose series, which may represent altered sediments. 

 Among these we may mention especially a peculiar rock which 

 contains tremolite, a colourless pyroxene, pyrrhotite, and abundant 

 distinct scales of graphite. 



The relations of the granulitic quartzite series to the gneissose 

 series and limestones are not yet made out with certainty, and it 

 would be premature to attempt a full description of them. The 

 quartzite series is repeatedly folded with the gneissose series, and 

 its boundaries are approximately parallel to the adjoining outcrops 

 of limestone. Thus, on first inspection of a geologically-coloured 

 map, the quartzite and the limestone appear as if they might be 

 parts of one great sedimentary series. Individual sections which 

 expose the junctions of the two sets of rocks fail also to show any 

 difference in the strikes of the foliations in the rocks. Yet it is 



1 In this paper the numbers applied to rocks are those of hand-specimens and 

 thin slices which belong to the Greologieal Survey of Scotland, and are pre- 

 served in the Museum of Practical Geology, Jermyn Street, London. 



