coos AND ESSEX DISTRICT. 73 



to the succession of rocks applies equally well to the granites in the re- 

 gion south of the Notch. On the north-west side of Mill mountain, half 

 way up, the porphyritc penetrates the dark siliceous schist, as also at the 

 Devil's Slide. Boulders from the Slide can be seen near Hickey's mill. 

 On the south-east side of Mill mountain the porphyrite comes in contact 

 with a schist that is similar to that which is found in contact with the 

 rock on the hill east of Groveton ; but here the schist is everywhere ver- 

 tical. As in the valley of Mill brook boulders of labradorite are common, 

 it is quite probable that this rock may be mostly covered up by the por- 

 phyrite. On the south side of the area, half a mile above the Waumbek 

 house and west of a small stream from the mountain, the porphyrite pen- 

 etrates the gneiss. The rocks that we have seen in contact with the 

 porphyrite are a siliceous schist almost a quartzite, a feldspathic chlo- 

 ritic schist, and gneiss. On the west we have the rock that is found 

 along the Connecticut, through Northumberland and Lancaster, which 

 was probably originally a sandstone, though its character as such is gen- 

 erally obliterated. This rock is everywhere on the west, and generally a 

 short distance from the porphyrite, but at the south end of Mt. Lyon it 

 comes in contact with it, and extends around on the south as far as Jef- 

 ferson. This is succeeded by a gneiss, — a rock that is extensively devel- 

 oped in Whitefield, — that extends through Randolph into Berlin. There 

 are several places where the gneiss comes in contact with the sandstone, 

 and underlies it. The rock on the north-east is a common granite, while 

 on the north there is a small area of a schistose rock, which is an argil- 

 laceous sandstone schist. 



Granite and Granitoid Gneiss. 



Rocks composed only of quartz, feldspar, and mica, and in the propor- 

 tions found in typical granite, are very rare in northern New Hampshire. 

 In the Atkinson and Gilmanton Academy grant there is a band of grani- 

 toid gneiss from half a mile to a mile in width, and it forms the height of 

 land between the Little Diamond and Magalloway. It is composed of 

 quartz, feldspar, and mica, both black and white, and is a rock of very 

 fine texture. On the west there is a narrow band of mica schist, and 

 this is succeeded by hydro-mica schist ; and on the east there is also a 



VOL. II. lO 



