TJREY. GEOLOGY. 47 



in Ben Hynish and Ben Hinivarr, and the 'paler ones 

 at the other. In many cases these pale varieties 

 consist almost entirely of felspar, or of felspar and 

 quartz ; just so much hornblende entering into them as 

 to give the linear appearance by which in a particular 

 direction gneiss is always to be distinguished, and 

 which forms in these cases its only ground of distinc- 

 tion from granite. Wherever the gneiss is visible, of 

 whatever composition it may be, it is almost always more 

 or less contorted or bent. Very rarely can a few yards 

 together be seen, of which the laminae are straight as 

 well as parallel. Yetij however disturbed, there is always 

 an indication of the laminar structure in some part or 

 other of the mass. 



This gneiss abounds in granite veins, and there is 

 great difficulty in ascertaining their forms. In many 

 cases they obviously run a long and determined course, 

 giving off lateral ramifications, and being accompanied by 

 visible shifts in the continuity of the beds of gneiss 

 which they traverse. In others they present irregular 

 lumps of different sizes, sometimes ramifying, sometimes 

 simple, but still attended with a confusion of the gneiss 

 in which they lie. They are often as abundant as the 

 rock which they traverse ; in many cases they even 

 occupy more space, fragments alone of the gneiss ap- 

 pearing among the intricacies of the granite. At times 

 they intersect each other so as even to produce a reticu- 

 lation of the general surface, their intersections being 

 sometimes attended with the shifting of one of the veins ; 

 while at other times they cross each other without any 

 change of direction in either. They differ somewhat in 

 composition, and it is one of their frequent characteristics 

 to contain larger concretions of one or other, or of all 

 their several ingredients, than ordinary massive granite. 

 In other instances, they are of so common a character, 

 that specimens taken from them would not be sus- 



