PLATE VII. 



A. Fine grained white gneiss (Vermont formation) from western slope Hbosac mountain. From 

 a microphotograph. Polarized light, x 33. 



In the large feldspar twin «. the line of twinning is oblique to the external planes of the crystal. 

 The little black or white runnel spots in it are grains of quartz which lie roughly in lines parallel to 

 the lines of arrangement of the quartz, feldspar, and mica outside. 



B. Gneiss (Vermont formation). Dump lloosac tunnel. From a microphotograph. Polarized 

 light, x 33. 



A large crystal of microcline (a) has been broken into five parts in the general crushing of the 

 rock, and the gioundmass, composed of little grains of quartz and feldspar and some mica, crosses 

 it by the cracks. 



