Fig. s, a and B. — Biotite garnet gneiss. (Magnification about 30 diameters. 

 Ordinary light.) The photograph (A) shows the garnets traversed by two sets of 

 fractures one of which is parallel to the schistosity. The dark areas along the fractures 

 are chiefly chlorite. The lighter colored dark areas, the location of which is indicated 

 on the diagram (B), some of which are very minute and parallel to the schistosity, are 

 biotite. 



