224 C. CALLAWAY ON THE GEAISLTIC AITD 



Grey orthoclase granite appeared on the other side of* this schist, 

 and fifty yards further on I came to a second mass of hornblende- 

 schist, succeeded by several others separated from each other by 

 granite, which sometimes penetrated the schists in veins. The 

 granite between the fragments of schists was similar to the variety 

 at the barrack, but was less coarse, and a linear arrangement of 

 the mica was not apparent in it. The last rock seen in this traverse 

 was a glistening mica-schist, which seemed to lie outside the 

 granite. 



Prom this examination it appeared to me perfectly clear that I 

 was on the margin of a mass of intrusive granite. This rock, 

 homogeneous in texture and composition, lay between irregular 

 fragments of schist, which displaj^ed a foliation-dip to the south- 

 east. The mica-schist being very fissile, the granite had passed up 

 foliation-planes ; but the hornblende-schist is very tough and com- 

 paratively non-fissile, so that the planes of least resistance are pro- 

 bably joints. There was not the slightest indication of a melting-up 

 of the schist, the lines of junction being quite sharp. But if a 

 general fusion had taken place, some of the hornblende-schist must 

 have undergone the process ; for its foliation-planes end abruptly 

 against the granite. We can hardly believe, however, that a rock 

 which is nearly all hornblende could have been melted up into a 

 highly acidic granite. The foliation in the granite I will discuss 

 further on ; and will simply remark here that, on the metamorphic 

 hypothesis, it is singular for granite in mass to be foliated, while 

 the narrow bands between the schist-fragments show no trace of 

 foliation. 



Section on Lough Greenan (fig. 1, south-east end, p. 223). 



Leaving the Gap, I now struck to the north-east along the eastern 

 slopes of the granite mass of Crockmore, and in one place collected 

 beautiful hand-specimens showing the contact between granite and 

 schist. I then attacked the scarp which overhangs the pass at the 

 south end of Lough Greenan. The lowest rock seen was hornblende- 

 schist, with a moderate S.S.E. dip, overlain by a lead-coloured, friable 

 mica-schist. We next come, after a short interval, to a band of 

 blue compact limestone, slightly micaceous, dipping E.S.E., passing 

 under hornblende -schist, these strata forming the steep escarpment 

 overlooking the south-eastern side of Lough Greenan, and being 

 surmounted by the quartzites and associated strata which rise into 

 the steep hills overhanging the eastern margin of Lough Salt. 



Prof. Hull places an unconformity between the lead-coloured 

 schist and the limestone, assigning the former, with the underlying 

 hornblende-schist, to the Laurentian, and the limestone and asso- 

 ciated rocks to the Lower Silurian. There is certainly a discordance, 

 as is indicated by the dips in my section ; but such local variations 

 of strike occur too often in this and other disturbed regions to 

 justify so important an inference. The strike in this district, a 

 little further from the granite, is to the S.W., and therefore not 

 agreeing with either of the strikes in the section, but coinciding 



