312 C. R. KEYES — EPIDOTE IN" ETtUPTIVE KOCKS. 



alike. That those must be original constituents, and not secondary 

 products, is indicated by — 



1. Its presence in perfectly fresh rocks or rock but slightly altered 

 by orographic movements. 



2. Its inclusion in sphene, one of the earliest <• ponents to crystal- 

 lize out from the molten magma. 



3. Its occurrence with sharply defined crystallographic i';\rr>, com- 

 pletely mantled by clear, unaltered biotite or feldspar, and giving shape 

 to some of the essential constituents of the granite. 



4. Its presentation in long crystals, broken and bent, and the inter- 

 stices and parted cracks filled with biotite, and often continuous with, 

 and optically oriented the same as, the surrounding black-mica crystals, 

 whose shape is partially given by the epidote. These fractures appear 

 without doubt to be protoclastic in origin. 



