556 STRATIGRAPHICAL GEOLOGY. 



The rocks on the south-east side of the lake are of the mica schist divi- 

 sion. The whole of Candia is occupied by this twisted gneiss, and most 

 of our observations relate to the ledges on the eastern slope. The dips 

 south of the railroad are generally to the south-east. To the south of 

 Manchester we find a large number of white ledges of this rock below 

 Bakersville, and on the south-west side of Cohass meadows, on the road 

 to Londonderry. Another ledge appears at the fourth mile-post on the 

 same road. It extends into Londonderry as far as R. White's and E. 

 Young's, with the dip south-east. These observations evidence the exist- 

 ence of a main anticlinal axis in this range, and are embodied in Fig. 92. 

 Passing to the west side of the Merrimack the rocks are found to cor- 

 respond with those already noticed. The twisted varieties are all on the 

 south-east half of the range. At Amoskeag falls one can examine a large 

 variety of ledges. The basis is a coarse mica schist, dipping north-west, 

 varying to N. 10° W. This contains four or five thick masses of very 

 coarse granite. The very conspicuous bosses of rock seen in the falls 

 consist of this latter variety. Smaller inconsequential veins may cut the 

 strata, like two of somewhat similar character near the west end of the 

 bridge. Some of the schists contain large egg-shaped nodules of a 

 quartzose character. The granite is often graphic, and contains tourma- 

 lines. The schistose rocks may also be well seen upon the island, a 

 quarter of a mile to the south. In Amoskeag are extensive ledges of 

 granite similar to that quarried to the north-east of the reservoir. There 

 is mica schist on the north side of Black brook. Near Rock Rimmon is 

 a ledge of coarse granite similar to that in the falls, and with it consider- 

 able of the finer grained material, which has been quarried. It is some- 

 what ferruginous. The dip is northerly and N. 20°-30° E. On climbing 

 the rock itself the material is seen to be distinctly gneissic, some layers 

 being very coarsely crystalline. On the south-east side the dip is S. 85° 

 E. ; on the south-west side the dip is N. 85° W, ; at the north end ^y" N. 

 The strata are often curved along the strike. None of the dips are the 

 prevailing ones, and the peak looks as if it had been subjected to rough 

 pressure. It is isolated by its situation in a sandy plain, — being the rock 

 seen so conspicuously to the west from the streets of the city opposite. 

 South of the Piscataquog river, in the village of the same name, we 

 observe first several ledges of the mica schist variety, dipping 65° north- 



