Geological ISfotcs fropi West Gahvay. 157- 



The mica appeans to occur in thin flakes rather than in the 

 usual nests, and on this account it frequently appears as small 

 rods on the broken surface of the rock. The granite veins 

 are all somewhat displaced by small faults. Pieces of pure- 

 looking quartz are common in the schist, which sometimes 

 appears to send veins into them. These may be due to silica 

 deposited in cavities left by the solution of pieces of limestone, 

 which were picked up by the schist when it originally invaded 

 the sedimentary rocks as an intrusive mass (see below). 



Cutting b^twkkn I^oughs Shindii,i,a and Oorid. 



A diagram of this cutting is shown in fig. 2. The average 

 depth of rock is about 12 feet. The eastern end is made up 

 of crushed quartzitic mica-schist, with perhaps some horn- 

 blende-schist and granulite. The joints usually contain much 

 chloritic matter. Proceeding westward, the schist becomes more 

 hornblendic. There are several patches of crystalline lime- 

 stone (X), more or less mingled with the schist. One of these 

 patches is entirely enclosed by the schist, and near it is a piece 

 of pure quartz with included patches of limestone. This sug- 

 gested to me the explanation of the origin of pieces of quartz 



Fig. 2. 



Bridge. 





in the last cutting described. Close to the bridge, which 

 carries the public road over the cutting, is a large vein of 

 normal granite. West of the bridge there is a remarkable 

 series of hornblende schists, which seem to have almost en- 

 tirely escaped the crushing action which affected the rest of 

 the cutting. The first of these is a fine-grained actinolitic 

 hornblende-schist (A), which Professor Cole, on microscopic 

 examination, finds to contain irregular patches of a pale 

 mineral, probably granular epidote ; also a minute sap-green, 

 isotropic granular mineral, of high refractive index, which 

 crystalised out early in the history of the rock. This is pro-, 

 bably a green garnet, but really requires separation with dense 



