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.PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[Feb. 20, 



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of the Caledonian Canal, as exhibited in the sections ; and the results 

 of my observations have induced me to conclude that on the main- 

 land the lower rocks of this section are not represented, and that we 

 have no metamorphic rock, either in na- 

 ture or arrangement, in this great area of 

 Scotland, that can be paralleled with the 

 " fundamental gneiss " of Sutherland and 

 Ross. 



§ 10. The Arrangement of the Metamor- 

 phic Rocks of the County of Donegal, and 

 Section of the East Side of Lough Foyle 

 (fig. 9). — On that portion of the Irish 

 coast which is most nearly contiguous to 

 the south-western extension of the quartz- 

 rocks and limestones of the Grampians, we 

 have a great development of rocks of a me- 

 tamorphic character. Almost the whole of 

 the County of Donegal is made up of rocks 

 which appertain to this series ; and with 

 them are associated plutonic masses. Of 

 the deposits in this area the greater por- 

 tion consists of gneissose strata, nearly 

 allied in lithology to the chloritic schists 

 of the S.W. parts of the Grampians. 



These chloritic schists, which in geolo- 

 gical maps of Ireland are generally termed 

 mica-slates, are subjected to great flexures. 

 They have prevailing N.E.-S.W. strikes ; 

 and, on the whole, S.E. dips are predo- 

 minant. Like rocks of a similar nature, 

 these gneissose rocks of the North of Ire- 

 land manifest themselves under such cir- 

 cumstances as to induce the conclusion that 

 they occupy the higher zone amongst the 

 deposits of this region. Beneath these 

 gneissose rocks of Donegal there is seen a 

 thick series of quartz-rocks, having the 

 same strike, and being subject to the same 

 flexures and dips as the overlying strata. 

 In many localities in the North of Ireland, 

 between the quartz-rocks below and the 

 gneissose strata above, there occurs a dark- 

 grey limestone ; and in some areas, where 

 the flexures become flattened, this lime- 

 stone covers a considerable surface. This 

 limestone, which is well seen at Culdaff, 

 on the N.E. side of the Inishowen penin- 

 sula, occurs in other localities between the 

 quartz-rocks and the gneissose beds, but 

 has hitherto yielded no fossils. 



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