158 The Irish Nattiralisi. 



liquids for its determination. In the schist are some wtitish 

 lenticular patches, which effervesce with acid, and appear to 

 be rolled-out fragments of limestone. A handsome schist (B), 

 with bronze mica and prismatic crystals of hornblende, 

 appears to cut the last. The joints of these schists contain 

 much chloritic matter, so as to form occasional lenticles of 

 chlorite-schist. Some intrusions of a remarkable granite 

 may be seen here. In general it is very felspathic, with 

 occasional large flakes of black mica (biotite). In places it is 

 compact in texture. Scattered through the mass are numerous 

 small dark inclusions. Professor Cole has examined a speci- 

 men of this rock under the microscope, and finds the dark 

 blotches to be actually much altered garnets. Some residual 

 garnets occur, in a soft green product that has formed all 

 along their cracks. A few pale pink unaltered garnets may 

 be found on careful search ; and some small cavities, to be 

 seen near the surface of the rock, appear to be left by the 

 destruction of the garnets. The garnet in this granite is pro- 

 bably all that remains of picked-up pieces of the schist, through 

 which it flowed. 



The rock marked c in the diagram is a schist composed 

 mainly of bronze mica with hornblende crj'stals. It weathers 

 easily into a micaceous mould, which forms a considerable 

 deposit around it. Professor Cole believes this rock to be an 

 altered diorite. Indeed, I think it not improbable that the 

 hornblendic schists to be seen here are simply the metamor- 

 phosed representatives of the diorites and finer associated 

 hornblendic rocks, which occur in the district south of the 

 great chain of lakes. 



Cuttings ai,ong Oorid I^ough. 



In the cutting nearest the east end of the lake, there is an 

 interesting granite intrusion in the schist. Fig. 3 is a sketch 

 of part of the right side. The portion marked B is a normal 

 granite with dark flakes near the edges, which appear to be 

 torn-off" portions of the schist. In the normal granite are 

 patches (A) of very coarse felspathic granite, with large flakes 

 of greenish mica, which appears to be much chloritised biotite. 

 The portion C that flows over the schist appears to be slightly 

 foliated. 



