﻿Vol. 66J\ ABOUND THE ROSS OF MULL GRANITE. 383 



inch up to 4 inches ; some close together and others as much as 

 6 inches apart (see fig. 3, p. 381). 



The intervening beds of schist are crossed, at an angle of about 

 25°, by a set of injections along strain-slips connecting those along 

 bedding. They are generally very thin white veins, in this case 

 from, say, 0*02 to 0*10 inch thick, and about a sixth of an inch 

 apart, but the dimensions vary considerably in different instances. 

 The resulting rock is a gneiss with banding in two directions, ot 

 which a specimen is shown, of the natural size, in fig. 4 (p. 384). 



(4) Injection along foliation has taken place to varying 

 degrees. Sometimes, as in the cases figured here, granitic matter 

 has penetrated between the folia of mica only a little way from the 

 margins of intrusions of the above kinds. Sometimes, especially in 

 the coarsely-rumpled quartzose pelitic gneiss, the intrusions are 

 definite separate veins, which may be traced for some distance 

 along the structure. The rocks forming the hill behind Bendoran 

 Cottage have been much affected in this way, but it is difficult to 

 discriminate between the injected material and the layers of quartz 

 and felspathic material belonging to the rock. Masses thus affected, 

 however, seem to lose some of their schistose nature, and wear like 

 the granite into rounded hillocks, rather than into the usual angular 

 and jagged crags. 



More commonly, the intrusions along foliation are in the finest 

 strings, threads, and films, woven inseparably among the mica-felts. 

 In extreme" cases the invading granite is in large proportion in the 

 rock, and has not only penetrated between the folia, but between 

 the individual mica-plates. Some considerable masses of rock are 

 permeated in this way. A good example may be seen by the shore 

 about a fifth of a mile south-south-east of Rudh' Ard an Daraich, 

 where a bed of quartzose biotite-gneiss, occurring in the quartz- 

 felspar granulit.e series, has been converted into a rather pale com- 

 pact rock weathering to a reddish colour, and somewhat resembling 

 a granitoid gneiss. 



Among blocks of schist included in the granite examples may 

 be found in every stage of transformation. Some have sharp 

 boundaries and are apparently unaltered, while others have been 

 so permeated that only the faintest outlines or ' ghosts ' can be 

 discerned. Probably the identity of many has been completely lost, 

 and here it may be observed that, although the normal granite 

 contains but little mica, the marginal portions along the line of 

 junction with the schists are comparatively rich in biotite. 



In some places a curious rock has been produced in small quantity 

 where very complete commingling of much schist material with 

 the granite has taken place, the schistose texture being obliterated. 

 It is speckled black and white, and contains a large proportion 

 of biotite. The rock is of medium grain, but rather large white 

 felspars, such as occur in the coarse granite, have crystallized out 

 with almost porphyritic habit in this micaceous ground- mass. The 

 best examples are 500 feet north-west of Bendoran Cottage and 



