SCHISTOSE E0CK3 OF NORTHERN DONEGAL. 239 



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ferred to the Laurentian system, is a true igneous granite, as seen in 

 its intrusion into the adjacent schists, in its inclusion of masses 

 and fragments of other rocks, and in its metamorphic action on 

 limestone in contact. 



2. This granite is distinctly foliated, the gneissic structure being 

 caused by lateral pressure (probably from the south-east), of which 

 there is evidence in the marked cleavage and intense contortion of 

 strata, in their occasional fractured and crushed condition, and in 

 the frequent overthrow of folds and overthrust of faulted masses. 



3. The granite is intrusive in a thick group of quartzites, quartz- 

 schists, hornblendic, micaceous, and talcose (?) schists, and crys- 

 talline limestones, called the Kilmacrenan Series. These rocks are 

 truly crystalline, but usually thin-bedded and fine-grained. 



4. The cr5'stalline schists are bounded on the east by a semi- 

 crystalline series, consisting of quartzose grits and itacolumites, 

 quartzites, crystalline limestones, compact dolomites, phyllites, inter- 

 laminations of grit and schistose matter, and finely foliated micaceous 

 schists. These may be designated the Lough-Foyle Series. 



DlSCTTSSION *. 



Mr. Etjilet remarked that there seemed to be no greater reason 

 for surprise at the inclusion of large masses of schists &c. in intrusive 

 granite than at the occurrence of small fragments, or " horses," in 

 dykes. In connexion with the change of limestone into garnets, 

 he inquired whether the limestone was siliceous or aluminous. He 

 also objected to the use of the term " mineralized grit," and inquired 

 what was to be understood by it. He doubted whether Dr. Sterry 

 Hunt's correlations ought to be accepted in the present instance. 



Mr. E. H. Scott bad hardly expected his paper to be exhumed 

 after the lapse of twenty-two years. He objected to the title of 

 Dr. Callaway's paper ; it should have been on part of the north- 

 west of Donegal instead of on the whole county. The granite of 

 Barnesmore was of a diff'erent type from that of the district 

 described in this paper, which is similar to that of Argyllshire. 

 When he had worked upon these granites microscopic examination 

 of rocks was not so well understood as it now is ; and he could not 

 investigate the rock thoroughly. He had not assigned any parti- 

 cular age to the granite, and he had expressly alluded to intrusive 

 veins, though he considered the rock to be metamorphic. There 

 were similar beds north-west and south-east of the granite in the 

 north, showing a possible anticlinal. He remarked that Dr. 

 Callaway would find work to do in the south of the county 

 and eastward in Tyrone. There are similar altered rocks through- 

 out this region, passing on to fossiliferous beds. There are two 



* Portions of this discussion relate to certain views, as to the correlation of 

 the rocks described, which were put forward at the conclusion of the paper, but 

 which were subsequently withdrawn by the author. 



