372 



FREDERIC 11. LAHEE 



plagioclase. Otherwise, in respect to size, abundance, ami arrange- 

 ment oi phenocrysts ami characters oi the groundmass, it is mega- 

 scopically like the type above described. 



The coarse psephitic rocks here contain fragments of whitish 

 ami drab schists, as at Young's Pond. 



The Parker Hill locality, — Por- 

 phyry schists, tuff-like schists, ami 

 psephite schists are here exposed in 

 a belt several hundred feet wide. 

 The porphyry schists are liner than 

 the Young's Pond type. Along the 

 road that crosses Parker Hill between 

 Lisbon ami Lyman villages exposures 

 near the top of the hill exhibit curi- 

 ous relations. A dark-gray schist 

 (called hereafter the Parker Hill dark 

 schist") is associated with a whitish 

 rock of the Lyman series. The latter, 

 which will be called the Parker Hill 

 white schist, in several outcrops, con- 

 stitutes a matrix in which are scattered 

 large and small irregular blocks and strip> 

 of the dark schist, many being greatly eon 

 torted. The phenomenon resembles intra- 

 formational pebbles in clastic material. 

 The white schist is of the texture oi a 

 medium sandstone. Quartz ami feldspar 

 are both abundant and the interstices 

 between the larger grains are tilled with finer 

 particles of quartz and feldspar, together 

 with secondary mica. The dark schist is 

 phyllitic. Some specimens of it have mi- 

 nute phenocrysts in a still finer groundmass. 



Fig, 3. Rounded plagioclase 

 phenocryst surrounded by ground- 

 mass. Enlarged 10 diameters. 

 The Large white areas arc due to 

 imperfections on the negative. 



FlG. 4.- broken quart/. 

 phenocryst. The curving 



lines indicate the arrange- 

 ment of mica laths. En- 

 larged id diameters. 



MICROSCOPIC DESCRIPTIONS 



Porphyry schist of the Young's Pond locality. — Thin sections of 

 the porphyry schist from near the schoolhouse northwest of Young's 

 Pond show a nearly uniform groundmass. The diameters of the 



