WARREN. — ALKALI-GRANITES AND PORPHYRIES. 



257 



porphyry). The feldspars show much the same characteristics as 

 those in the Rattlesnake type, except that there is a stronger devel- 

 opment of the y, 201 face, with a corresponding approach to the 

 "rhomben" type of habit, and that the later additions of groundmass 



I'-'-M Contact PorfikijT^ 



l"'"'l Rh„ml,r,}.crf,h^ry. 



I^' = -~I Af„»hy<>Ute 



\DiabascD,ke. 



\ Slate 

 .. — ^- StantU/allt 



IV. .!' Path, t, Rontii 

 »'* XcnoliUs ^''/^ 



Special Map of the Pine Hill Area, West Quincy, Mass. 



This map is based on an outcrop map made for the writer under his 

 direction by Mr. J. D. Mackenzie, to whom the writer is indebted for a 

 painstaking piece of work. The patches of the rhombenporphyry and slate 

 have been purposely exaggerated in size, as have also the xenoliths, in order 

 to have them show on a map of this scale. Many more small xenoliths are 

 scattered through the granite elsewhere in the field but have been omitted 

 from the map. The southern portion of the area has a general elevation of 

 about fift}^ feet above that of the northern half. While the surface is extremelj' 

 rough, the actual differences in elevation are inconsiderable. 



