526 STRATIGRAPHICAL GEOLOGY. 



with it, thus necessitating the supposition of an antichnal east of the north- 

 ern village. The east part of the town of Antrim is occupied by a later 

 gneiss, supposed to be encircled by the coarser rock, and to be that which 

 crops out at first north of South Antrim and continues to Bennington, on 

 the west side of the Contoocook. At Bennington the strata are about 

 vertical, and the strike runs north-east and south-west. The rock at the 

 mills in the village is well characterized. Hancock is entirely underlaid 

 by porphyritic gneiss, and the whole breadth of the formation is repre- 

 sented by the town limits. To the south it narrows rapidly. A trip up 

 Nubanusit river, into the east part of Dublin, showed only drift ; but near 

 the north-west corner of Peterborough there is a hard rock associated 

 with porphyritic gneiss, dipping N. 50° W. The ledges were seen at 

 intervals for two miles parallel with the north town line. 



There is a spur of the porphyritic gneiss running from Peterborough 

 into Greenfield and Francestown. An enormous boulder of it first 

 attracts notice at J. Miller's, near the Greenfield line, — no ledges appear- 

 ing from Peterborough village till we come to A. Green's. The country 

 is flat, and covered with glacial drift much of the way, with a very few 

 rocky outcrops. In Francestown the eastern limit of the porphyritic is 

 reached near S. Duland's, the ferruginous seams there indicating a posi- 

 tion of 50° N. 85° W. It is noticeable that this branch points towards 

 the large porphyritic area in Weare, and an axial line is probably indi- 

 cated by this circumstance. The areas of this rock farther south, in 

 Jaffrey and Fitzwilliam, have been noticed in the previous chapter. 



Upon Plate I there is a small area of this rock represented in Massa- 

 chusetts, occupying the natural extension of the main New Hampshire 

 range. The observations were taken from the Massachusetts report, 

 where we find both our northern ranges noticed. The more western one 

 shows itself in Northfield. The more eastern is said to be situated imme- 

 diately east of a range of hornblende slate, which is made to extend from 

 the Connecticut line at Monson directly north to Royalston. It will be 

 noticed that Royalston adjoins Fitzwilliam; so that the connection 

 between the Massachusetts and New Hampshire main ranges of this 

 ancient rock is clear, and the general north and south course of the range 

 is also continuous. My father thinks a strip of it may be found extend- 

 ing as far south as Long Island sound. He speaks of the fine develop- 



