GEOLOGY OF THE MERRIMACK DISTRICT, 52$ 



extremely common along the Mink hills, and the country west and south 

 to the town lines of Bradford and Henniker. The road from the North 

 branch in Antrim, across Windsor to Washington, shows chiefly ledges 

 of porphyritic gneiss. The first hill climbed is very steep, and the strata 

 may dip north-west. After reaching the crest of the hill, ledges are not 

 abundant, the surface of the country being mostly covered by immense 

 boulders of the same material, particularly between the southern school- 

 house and Black pond. It is a characteristic feature of the porphyritic 

 region that the surface should be conspicuously covered by large boulders 

 of the same material with the underlying rock. Fertile tracts of land 

 occur where the covering of drift has been finer than usual, or they have 

 resulted from the filling up of low grounds. By Black pond in Windsor, 

 the strata dip south-east. The road through the northern half of Wind- 

 sor is over a smooth drift ridge, descending to a deep and wide alluvial 

 peaty flat, below the outlet of White pond. This water flows north- 

 easterly, tributary to the Contoocook, though not so represented upon 

 the county map. In the edge of Washington, the profusion of boulders 

 of porphyritic gneiss recommences, and the ledges appear at school-house 

 No. 6. Near here are a few ledges of common gneiss, followed very 

 speedily by the ordinary coarsely crystalline variety, which occurs several 

 times on the road to Washington centre. Hills to the east, like Kings- 

 bury, in Washington, and those in the east and north part of Windsor, 

 seem to have the same underlying rock. 



The next section (Fig. 86) extends from Stoddard to North Branch vil- 

 lage, in Antrim, the strata appearing mostly monoclinal without any anal- 

 ysis of the dips. As in Washington, farther north, quite ferruginous schists 

 flank the porphyritic gneiss on the west side, dipping 60° S. E., near Stod- 

 dard centre. At the mill village are the first porphyritic ledges, dipping 

 in the same direction. These ledges are magnificently displayed near the 

 east line of Stoddard. We have not passed directly over Tuttle hill, but 

 followed the road to the north, down the North Branch valley, where we 

 observed ledges of this rock at S. Dinsmore's and near the village. Its last 

 outcrop on the section line is near Campbell pond, on the west side of Mt. 

 Riley. Between the North Branch and centre villages are several outcrops 

 of this rock seeming to dip N. W. The gneisses of Mt. Riley dip easterly, 

 and therefore we represent a dip of the porphyritic variety conformable 



