WARREN. — ALKALI-GRANITES AND PORPHYRIES. 331 



substance attached to the phenocryst. The groundmass consists of micro- 

 perthite and pjToxene with some hornblende. 



Microphotograph, plane light. Magnification about 15 diams. 



Fig. Vlllb. — Same crystal as in Figure Villa but with crossed nicols. The 

 attached border of microperthite of groundmass age is well shown. 



Fig. IX. — Rhombenporphyry, Pine Hill Area, West Quincy. This shows a 

 composite feldspar phenocryst, the acutely terminated points of the crystals 

 pointing the same way. The development of minute pyroxene microliths in 

 the marginal growth of feldspar just outside the boundary of the original phen- 

 ocryst is well shown. 



Microphotograph, plane light. Magnification about 15 diams. 



