Granites from British Columbia, etc. 345 



of mica have been developed. Similar rocks are found 

 on other parts of the coast, both in the north and south, 

 and from a lithological point of view, they much resem- 

 ble the Triassic argillites of the Queen Charlotte Islands, 

 though no fossils are found at this place. The ridge 

 behind the town of Wrangell is chiefly composed of rather 

 fine grained grey granite, which is probably intrusive and 

 may have been the cause of the incipient crystallization 

 observed in the argillites. The north part of the island is 

 formed of a similar granite, probably a continuation of the 

 same mass." Dr. Dawson informs me that the granites all 

 through this district seem to be more recent than the slates 

 and that he regards the mass in question as almost certainly 

 of eruptive origin. 



The hand specimen when examined seems to show a 

 very indistinct tendency towards parallelism of mica 

 individuals, and when thin sections are examined there is 

 evidence in the somewhat uneven extinction of the quartz 

 grains as well as in the twisting of the biotite, that the 

 rock has been submitted to pressure. It is composed essen- 

 tially of quartz, orthoclase, plagioclase and biotite, with 

 epidote, allanite, garnet, sphene, zircon and apatite, as 

 accessory constituents. The essential constituents show 

 nothing especially deserving of mention. The feldspars 

 are generally fresh and frequently show a beautiful zonal 

 structure due to growth-rings. Occasionally a distinct bor- 

 der with well marked granophyre structure is seen about 

 a portion of a feldspar individual. The garnet, of which a 

 few grains are present in most of the sections, is light 

 brown in colour. The interest of the rock centres in the 

 epidote with its associated allanite. 



The epidote is present in considerable amount and is 

 generally associated with the biotite. It is colourless and 

 has rather a high index of refraction, occurring in prisms 

 elongated, parallel to the b axis with a perfect cleavage 

 parallel to the length. Examined in convergent light 

 between crossed nicols it is seen to be biaxial, the plane of 

 the optic axes in all cases being at right angles to the 



