GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. 23/ 



and it is all represented by a single color. Further exploration would 

 enable us to subdivide this upper portion. The lower eminence to the 

 left of Pequawkct is now called Bartlett mountain. 



In the ascent up the bridle-path west of the slate ledge, one remarks 

 the presence of trap-like fragments in the Albany granite; and, before 

 reaching the breccia, there are a few feet thickness of a fine-grained 

 quartz-porphyry, in which both the quartz and orthoclase occur as dis- 

 tinct and perfect crystals. The first part of the breccia, — perhaps one 

 hundred feet, — is almost entirely composed of slate fragments, insomuch 

 that a search with a lens is needful to discover any cementing feldspar or 

 quartz. In the midst of the breccia, also, there is either a ledge of slate 

 or a fragment thirty feet thick, dipping east, in the same direction with 

 solid masses of the same material higher up the mountain in the path. 

 The path lies to the west of the chief mass of the slate, on the south side 

 of the mountain. As the strata dip east along the path, there is evi- 

 dently a synclinal axis in the mass of slate. As we ascend the mountain, 

 the proportion of slate fragments in the breccia diminishes. The other 

 rocks present are white quartz, probably from veins in the slate, and 

 several varieties of porphyry. As the cementing material begins to pre- 

 dominate, it slightly resembles the Albany granite, with the porphyritic 

 aspect indicated by crystals of feldspar somewhat less distinct. Occa- 

 sionally the resemblance will be so great as to excite the query whether 

 the Albany and Pequawket granites are not identical. 



The following is a list of the specimens obtained in a section (VITI) 

 over Pequawket and Bartlett mountains, which may illustrate better than 

 a protracted description the succession of lithological variety. The first 

 one named comes from the east side, it being the first ledge succeeding 

 the Montalban system in Chatham. 



6. Albany granite — orthoclase crystals, one fourth to one half inch in length ; a 

 small amount of amorphous quartz, and a dark pepper-and-salt base. From the east 

 base of Pequawket, one mile east of the west line of Chatham. 



7. Porphyry — dark slate-colored base ; crystals of quartz and orthoclase dissemi- 

 nated, and scattered fragments of uncommonly flinty compact feldspar, from one twen- 

 tieth to one half an inch in diameter. From near No. 6. 



8. Porphyry — gray base or paste ; crystals of quartz and orthoclase present ; black 

 fragments very conspicuous, on account of the contrast in color between them and the 

 base, usually one fourth of an inch in size, and much like a granular slate. From the 



