Coi.E — On Composite Gnemes in Boi/lagh, Went Doiicfjal. 213 



consolidation occurred under the very influences that had driven it 

 from its subterranean caldron.^ But the continuation of these prcssui'es, 

 when consolidation had begun, broke up the tiny sheets of granite, 

 squeezed the yielding layers of biotite-schist between the crystals, 

 and gave us the interesting povpliyroide of Carbane as a parallel with 

 the "crush-conglomerates" that occur so often on a larger scale. 

 But, here again, the essential intermixture of materials occui-red 

 during the igneous flow. In one specimen, a lump of biotite-epidote- 

 gneiss occurs among the schist-layers, shifted by the dynamo-meta- 

 morphic movements from the position it once occupied, but showing 

 that gneissic rocks had arisen in Carbane by intermixtiu'e prior to 

 these particular movements. 



All the rocks examined from this contact-zone show signs of 

 pressure-alteration subsequent to their having received a foliated 

 structure. Were not the evidence satisfactory in the field, it would be 

 easy to attribute the principal foliation also to dynamic action. This 

 combination of igneous penetration with shearing movements seems 

 a common feature along granite-contacts in the Pyrenees.^ But 

 again and again, even in hand-specimens, we see that no dynamic 

 movements could have produced such differentiation in successive 

 layers of the rock. This is markedly the case in certain epidiorites 

 of the Dalradian series, which are found on Carbane delicately inter- 

 foliated with wavy and fluidal sheets of aplite. The final movements 

 have faulted some of these sheets, and the planes of fracture cut 

 across their foliation (PI. ii., fig. 1) ; but the original igneous inter- 

 penetration, and the consequent production of a hornblende-gneiss 

 with strongly differentiated layers, are as clearly traceable here as in 

 the instance elsewhere cited by me from Cregganconroe, in the county 

 of Tyrone.^ Sphene and epidote occur in the composite rock ; and 

 the latter mineral, occasionally appearing in large patches in the 

 fluidal granite veins, is doubtless there of primary origin, owing to 

 the conditions under which the ultimate consolidation of the rocks 

 took place.* 



^ Compare Weinsehenk on the Alps, Congres geol. internat., Coniptcs rendus, 

 viii'^' session, p. 340. 



^ See Lacroix, " Le granite des Pyrenees et ses phenomenes de Contact," l'^' 

 mem., pp. 6 and 40, and 2™'^ mem., p. 18. 



'^ " Metam. Eocks in E. Tyrone, etc.," Trans. E. Irish Acad., vol. .xxxi., 

 p. 440, and pi. xxvi., fig. 1. 



* See Weinsehenk, "Memoire sur le dynamometamorphisme, etc.," Congres 

 geol. internat., Comptes rendus, viii*^ session (1901), p. 310. 



