276 STRATIGRAPHICAL GEOLOGY. 



than that of the newer formations upon both sides. Hence it is believed 

 there is an unconformity, the older rock really possessing a greater angle 

 of inclination, as we must add to its present dip 90"^ for inversion. The 

 hill east of North Lisbon is covered heavily with drift; and explorations 

 have not been made extensively away from the road, so that our dip 

 observations there are scanty. 



The upper layers, or outer border of this area, are different from the 

 characteristic Bethlehem rock, containing an abundance of black mica in 

 place of the chloritic mineral, and occasionally lacking an abundance of 

 feldspar. Some layers are epidotic. In my first article this narrow outer 

 band was referred to the next division of gneiss. It is better to place it 

 in the Bethlehem group, partly because of its recurrence in the older 

 rock in terranes lower down on the Connecticut river. The map shows 

 a small outcrop of this member just below the mouth of Salmon Hole 

 brook, nearly on the line of the continuation of this formation. I have 

 sometimes thought it passes from this locality to the Atwood gold mine, 

 a mile east of Lisbon village. The dip at the first-named place is in- 

 verted. As the same formation appears in Haverhill, it may be contin- 

 uous near the surface from Bethlehem, If so, it may determine axes in 

 the later formations. 



2. Atlantic Gneiss. 



This belt is the south-west continuation of the Berlin-Randolph and 

 Whitefield ranges. The first lies mainly to the east of the Coos group 

 in Lisbon and Landaff, belonging to the territory assigned to the Merri- 

 mack topographical district. The latter is nearly cut off by the Wing 

 Road porphyritic gneiss, and spreads out more largely in the east part of 

 Littleton. The village seems to lie upon it, though covered by coarse 

 drift, and having micaceous c|uartzites in the river. Mann's and Oak 

 hills furnish the first exposures of this gneiss. No evidence of its exist- 

 ence beyond Parker brook has yet been discovered. The narrow band 

 of gneiss in Fig. 27, encircling the Bethlehem gneiss from Factory vil- 

 lage to North Lisbon, and thence beyond Streeter pond, is included with 

 the latter formation constituting its upper member. The north-westerly 

 dip is universal over the western area of this gneiss. There is first its 

 representation on Fig. 11 for Whitefield. Between Bethlehem Hollow 



