SCHISTOST] ROCKS OF NORTHERN DONEGAL. 229 



would be " hardly possible," if the rock had been in a " state of 

 simple fusion." But the ^anite has been in a state of fusion on 

 either hypothesis, and yet the oligoclase in the presence of quartz 

 has declined to pass into a more acidic felspar. Whether or not the 

 granite was once stratified rock does not matter if fusion has actually 

 been produced. 



But the evidence which Mr. Scott most strongly urges is that — 

 (4) " Far within the limits of the granite " occur " isolated patches 

 of metamorphic rock, not lying on the granite, but in it." 



This fact is in perfect harmony with the igneous theory. "Why 

 should not fragments of rock sink down into a molten mass ? Or 

 why shonld not fused matter rise up round masses of schist ? If 

 the granite was squeezed up through rocks which were traversed by 

 faults and joints, it would probably carry up some masses before it 

 and become entangled amongst others. The former would be the 

 first to be removed by denudation, so as to expose the subjacent 

 granite, amidst which fragments of the stratified rocks would be 

 preserved. 



The Author's Objections to the Metamorphic Hypothesis. 



(1) If the granite is simply a metamorphosed portion of a mass 

 originally sedimentary, we should expect to find it graduating into 

 the adjacent schists and limestones. But I have been unable to detect 

 the least evidence of such a passage. The numerous junctions I have 

 seen have been quite distinct, or there has been a slight welding to- 

 gether of the two rocks. Prof. Bouney has microscopically examined 

 sections selected by me as showing the contact of granite with schist 

 — one from Bunbeg, where the granite is unfoliated, and one from 

 Barnesbeg Gap, in the foliated region — and he quite agrees with my 

 interpretation. At Bunbeg pieces of schist no larger than a man's 

 hand are immersed in granite, yet their margins are quite sharp. 

 This surely would be an impossibility if these fragments were merely 

 the unmelted remnants of a series which had undergone partial 

 fusion. On the other hand, these appearances are not uncommon 

 where igneous rocks have been intruded into stratified rocks. For 

 example, on the same coast, near Horn Head, the diorite at one spot 

 is crowded with fragments of contorted schist. 



(2) A. uniform mass of granite could not have been produced by 

 the fusion of a varied series of strata, including quartzite, quartz- 

 schist, micaceous and hornblendic schists, and limestones. There 

 would surely be bands in the granite corresponding with the mate- 

 rials out of which they were formed. The chemist, too, would be 

 curious to know how granite could be produced by the melting of 

 quartzite, or limestone, or hornblende-schist. I admit variations in 

 the granite, but these give no support to the metamorphic hypothesis. 

 Thus, the granite of Barnesbeg Gap, associated with micaceous and 

 hornblendic schists, is mainly composed of quartz and orthoclase ; 

 while in the granite of Dunaff Head, surrrounded by quartzite, pla- 

 gioclase predominates, and there is a fair amount of mica. 



