BY THE REV. J. MILNE CURRAN. 213 



polarizer is rotated. There are also a few crystals of hornblende, 

 which is also strongly dichroic ; but, as has been already explained 

 in a former portion of this paper, there is little danger of con- 

 founding the two minerals. The orthoclase felspar is cloudy, 

 appearing of a snowy white by reflected light. The hornblendes 

 contain some bright green patches of decomposition matter. 



2. (Slice 38). This slide contains a hornblende crystal 4*6 mm. 

 along its vertical axis. The largest patch of quartz is 2 mm. by 

 1*8 mm. Triclinic felspars are present showing a beautiful 

 banded structure under crossed Nicols. The quartz is clear and 

 limpid, containing few inclusions other than the fluid cavities. 

 The hornblende and biotite are the only minerals showing 

 traces of boundary planes. 



3. (Slice 34). The minerals present are quartz, biotite, felspar, 

 orthoclase, and triclinic felspar. Fluid cavities are very plentiful 

 in the quartz, numbers coming into the focus of the glass as the 

 different planes are reached by the fine adjustment. The felspars 

 are in places almost impellucid. A few crystals of magnetite are 

 included in a flake of biotite. 



4. (Slice 37). Under the microscope some finely striated, clear 

 brown mica is seen. Even in the thinnest section it is strongly 

 dichroic. When the cleavage lines are parallel to the plane of 

 vibration of the light, the sections are black or very dark brown. 

 A few crystals of apatite are enclosed in the quartz and biotite. 

 A reddish-brown wedge-shaped sphene will be noticed on the 

 margin of the slice. The biotite alters to a leek-green material 

 that often preserves the dichroic character, but the cleavage lines 

 are lost. The felspars as is usual are impure and cloudy, and the 

 quartz beautifully pellucid. The hair-like microlites, to which 

 reference has been already made, are abundant. Triclinic felspar 

 is present, but not so plentiful as orthoclase. 



Chemical comjyosition of the Granite. 



Specific gravity at 18-5° C 2-85-2-93 



1 am indebted to Mr. Mingaye, F.C.S., of the Geological Survey 

 Laboratory, for the following analysis of the granite. The 



