CoLK — On CoDiposifc Gneisses in Boylayh, West Donegal. 221 



various other places in Boylagh, as we have already notod. Dr. Callaway 

 held that the main gncissic structure was due either to igneous flow 

 of molten material, or to flow of some kind under earth-pressures. 

 The latter type of flow might have occurred — (i) during consolidation, 

 or (ii) after consolidation. Dr. Callaway^ concluded in favour of 

 dynamic met'amorphism after the granite had forced its way as an 

 intrusive rock among the schists. 



It was in the light of these previous opinions and observations 

 that the officers of the Geological Survey approached the interesting 

 area between Maas and Finntown. Mr. A. M'Henry,^ in noting the 

 masses of limestone and schist caught up here and enveloped in the 

 granite, explains their parallelism with the foliation in the igneous 

 rock by stating that " both the granite and enclosed masses have been 

 subsequently foliated at the same time by the last great shearing 

 forces that affected this region." 



In a previous section of the present paper, on the other hand, 

 certain foliated granites towards the Maas end of the district have 

 been explained as due to imperfect incorporation of the hornblende- 

 and mica-schists in the igneous rock (p. 216). Mr, J. A. Cunningham, 

 B.A., A.E.c.sc.i., who accompanied me throughout these observations, 

 subsequently visited the foliated granite on the road from Glenties to 

 Doocharry Bridge on the south side of the Gweebarra. A photograph 

 taken by him shows how much work remains to be done on the non- 

 homogeneous " banded gneisses" which are boldly developed across 

 this area. At present, however, I propose only to furnish details from 

 personal observation on the historic roadside sections between Glen- 

 leghan (Glenleheen) and Einntown. I am willing, however, after 

 experience of similar materials in the Pettigo area, to take these 

 exposures as representative of a much wider district. 



On approaching Glenleheen by the highly picturesque road from 

 Doocharry Bridge, the intrusive character of the granite is manifest 

 at the top of the long rise from Adder wal, and just within the town- 

 land of Meenmore West. The granite has penetrated the schist along 

 the foliation-planes, and has converted it into a " leptynolite," in 

 which felspars are visible to the naked eye. A band of limestone, 

 marked upon the Survey map, is included in the granite, and has 

 undergone the usual type of metamorphism. Ked garnet, diopsidc 



1 Quart. Journ. Geol. Soc. London, vol. xli. (1885), pp. 230 and 2o9. 

 - Mem. sheets 3, 4, 15, etc. (1891), p. 69. 



