Cole — On Cofiipoai/e Gnomes in Boijlagh, Went BoneijnL 223 



marginal, and are due to slieets of scliist entangled in it. Mr. Scott' 

 aptly compared this type of gneiss near Finntown with the veins at 

 Castle Caldwell on Longh Erne ; I have little doubt that in both 

 localities these coarser granitoid rocks belong to the later series of 

 granitic intrusions. They may thus be of Devonian age. 



"When, however, these coarser rocks associate themselves with the 

 earlier and more fine-grained granites, as they do also at Carn, near 

 Pettigo, the composite rock formed of hornblende- or mica-schist, 

 penetrated along its foliation-planes by coarse and fine parallel veins, 

 presents a remarkable imitation of many Archaean gneisses. Yet it 

 owes its characters to the original flow of granite under pressure up 

 the most easily found planes of parting. 



Again and again, the shrinkage of the original uptilted sediments, 

 as metamorphism went forward, a feature on which Mr. Joseph 

 BarrelP has laid considerable stress, may have helped the intrusive 

 mass to spread upwards from below. The previous crumpling and 

 compression, however, of the Dalradian series probably drove off a 

 part of its volatile constituents, and so prevented any further marked 

 reduction in bulk under the heating action of the granite. 



Short of the local bands of pseudo-Hebridean aspect, we have 

 every variety of intermingling between the granite and the schist. 

 Biotite is developed in these grey gneisses and granites, partly at 

 the expense of hornblende. The epidote of the partially absorbed basic 

 rock remains intact, in association with much biotite, a little green 

 hornblende, and sphene. These minerals are grouped in flakes and 

 patches, which give the rock its gneissic aspect. The sphene is so 

 prominent in some of these mixed rocks that it has probably developed 

 during the epoch of contact-metamorphism. The rock-section selected 

 for illustration (PI. iv., fig. 2) shows foliated structure on a conve- 

 niently small scale ; otherwise it represents the more granitoid and 

 less basic type of the composite gneiss of Loughuambraddan. The 

 specimen from which it was cut shows a granite vein penetrating the 

 schist, and losing its identity in so doing, thus affording a complete 

 parallel with some of the specimens from Carbane. 



Another of the grey composite rocks examined in detail has a 

 specific gravity of 2 '74. It is, when considered apart from its mode 

 of occurrence, a member of the Tonalite series, with zoned orthoclastic 

 and plagioclastic felspars, quartz, biotite, hornblende, epidote, and 



1 Op. cit., Journ. Geol. See. Dublin, vol. x., p. IS. 



- " The Physical Effects of Contact Metamorphism," Am. Journ. Sci.,vol xiii., 

 (1902), p. 294. 



