642 MESSES. J. HORNE AND E. GREENLY ON [NOV. 1896, 



full of inclusions of all sizes, up to 100 feet long, round and between 

 which the granite passes in gently undulating curves, retaining its 

 own independent foliation, which often truncates that of the 

 inclusions. 



In Strathy Bay sills of very massive grey rock, with clear fresh 

 oligoclase and a beautiful waxy lustre, are seen. The junctions are 

 perfectly exposed, showing forms intermediate between sills and 

 dykes (fig. 2, p. 641). "Within this mass granites indistinguishable 

 in hand-specimens can be seen to vein each other, both rocks being 

 independently foliated. 



Both at Strathy and Portskerry, the whole foliated series is 

 traversed by dykes of pink microgranite. They are unfoliated, 

 and, though compact, have no chilled edges. They cut all the other 

 rocks very sharply. 



IV. KlNBRACE AND KlLDONAN AREA. 



Although the exposures in this district are far less complete than 

 those on the northern coast, they have especial interest, because the 

 less altered condition of the rocks at Kildonan allows us to see that 

 some, at any rate, of the crystalline schists into which the granites 

 have been introduced must be of sedimentary origin. 



The following groups or types can be distinguished : — 



1. Quartz-schist. 



2. Granulitic biotite-schist. 



3. "Wavy mica-schist. 



All these are truly crystalline schists, composed of interlocking 

 minerals ; the structure of Nos. 1 and 2 being that of a granulitic 

 mosaic. 



There can, however, be no doubt that No. 1, at any rate, is a 

 highly altered quartz-felspar grit. Not only are clastic grains 

 clearly recognizable in certain parts, but the highly quartzose 

 character, maintained over a large area, makes its sedimentary origin 

 practically certain. There are always some felspar and white mica, 

 and seams of iron ores are a characteristic feature. 



Group 2 resembles the granulitic schist of Portskerry, differing 

 only in that a few bands contain muscovite as well as biotite. But 

 its relations to the quartz-schist throw light on its origin. Not only 

 do seams of Group 2 occur constantly within the main mass of 

 Group 1, but the main masses of each always pass one into another 

 through a series of alternations in such a way as to leave little 

 doubt of their common origin. The boundaries on the map are, 

 indeed, quite arbitrary, and it is often difficult to decide how to 

 colour the intermediate types. 



Group 3 is different in texture. It is a very wavily foliated 

 schist, composed of both micas, quartz, and felspar (sometimes cer- 

 tainly oligoclase). The micas are much larger than in the granulitic 

 rocks, and the biotite is a deep brown ferruginous variety. Garnet 

 and sillimanite are generally present. The sillimanite is usually in 

 the mica, but sometimes in quartz (FaserhieseT) . This group passes 





