GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. 1 03 



The relations of the group to the adjacent Montalban schists, in a sec- 

 tion from West Thornton to Welch mountain, are shown in a figure 

 farther on. 



From Woodstock centre the porphyritic gneiss branches off south- 

 westerly into Ellsworth and Rumney. That occurring in Ellsworth will 

 be described under Section VII. In the north-east part of Rumney, at 

 a lead mine, the dip is 80° N. 72° W. To the south this range is entirely 

 covered by the mica schists of a much later geological age. 



TJie eastern range. The northern extremity of a very crooked range 

 of porphyritic gneiss enters the limits of the White Mountain from the 

 north-east corner of the Merrimack district, continuing for ten miles, 

 where it is concealed by later formations. It reappears in the deep valley 

 of Sawyer's river, about five miles north-easterly from Cascade brook in 

 Waterville, which is the extreme northern limit of this range in New 

 Hampshire. A spur runs easterly from this range along the south line 

 of Waterville towards Chocorua. 



Section VIII crosses the Sawyer's River outcrop of this rock. The 

 most satisfactory exposure is represented by numbers 58 and 59, from 

 the mouth of Carrigain brook. The water falls twenty-five or thirty feet 

 over the smooth ledges of this rock, which seems to dip 75° N. 68° E., 

 cut by a six-feet dyke of reddish feldspathic rock. These exposures 

 show large crystals of a somewhat flesh-colored orthoclase in greater 

 abundance than usual ; and there are many small bunches of amorphous, 

 nearly transparent quartz. The rock rings when struck by the hammer. 

 The width of the range must be two miles along this valley. This rock 

 comes up next on Cascade brook in Waterville. The cascades are of 

 granite ; but about half a mile above them the porphyritic gneiss appears, 

 with a northerly dip, but the strata are greatly contorted. At two miles 

 above the cascades the dip is 75° N. 80° E. This exposure shows amor- 

 phous quartz like that on Sawyer's river. None of the other specimens 

 from Waterville have this mineral present. Those from near the cas- 

 cades and the summit of Black mountain do not display the large crystals 

 of feldspar. We have no observations respecting the dips of this rock as 

 it is exposed just east of the Greeley hotel, the top of Snow's mountain, 

 Flat Mountain pond, the country between the last two mentioned locali- 

 ties, nor of the large areas of this rock on the western side of Black 



