640 



MESSES. J. HOENE AND E. GEEENLY ON [Nov. 1 896,, 



be mapped occupying about one-third of the surface in the well- 

 exposed parts, while the smaller outcrops are innumerable. 



The relations to the various types of schists are slightly different. 

 The granites and the granulitic rocks, however intimately inter- 

 banded, are sharply distinguished from each other. The cliffs of 

 Portskerry display a strongly banded series (fig. 1), composed of rapic& 



Pig. 1. — Gneisso-granitic complex, Budha Ghoiridh, Portskerry.- 



A = Gneiss. B = Granite. 



The granite is slightly foliated. 



alternations of grey granulitic schist and pink granite, with here and 

 there lenticular sills of foliated porphyritic granite from 2 to 3 yards 

 thick. The thin bands are true veins, for though at first sight con- 

 formable with the gneiss, they can be proved to truncate its folia 

 and to anastomose. Of their connexion with the granites there- 

 can be no doubt, for the whole series is traversed by precisely similar 

 veins at right angles, which can be seen to be continuous with some 

 of the bands, while cutting others. These veins usually lie along 

 planes of dislocation which fault many of the granite-bands, but 

 these old faults are completely * healed up,' the crystals interlocking 

 along them, and there being no sign of cataclastic structure. 

 With regard to foliation : 



1. The granite is almost always foliated, the structure being 



marked out, not only by the orientation of the mica-flakes, 

 but by that of the porphyritic felspars. Sometimes there- 

 are felspar * augen,' and even bands, the whole mass being 

 there very complex. But generally the felspars are angular,. 

 and even zonal. 



2. The foliation usually follows the cheeks of the sill or vein. 



Sometimes it is discordant to that of the schist ; sometimes 

 it folds rapidly, without the sill folding as a whole ; and again 

 here and there, though rarely, a foliation parallel to that of 

 the schist appears to pass through a vein. Finally, in the- 



