496 STRATIGRAPHICAL GEOLOGY. 



pond, and when it comes in contact with the porphyritic gneiss it rests 

 unconformably on it. The porphyritic gneiss does not He entirely to the 

 east of the fibrohte rock, but there are several small areas where it is 

 entirely surrounded by it. One is on Moulton brook, where the road 

 crosses it at H. & D. Sanborn's mill; and there are two in Rumney, — one 

 west of Stinson pond, and another on the north side of Stinson mountain. 

 This is probably the extension southward of the large area at Ellsworth 

 pond, most of the porphyritic gneiss being covered up by the fibrolite 

 rock. As the areas of porphyritic gneiss to which we have referred are 

 nearly equidistant from each other as far as the strike of the rocks is 

 concerned, it seems altogether probable that they constitute a synclinal 

 axis underlying the fibrolite rock ; and it is possible that this may give 

 us the data for determining the actual thickness of the latter. 



In Rumney, except the small area of porphyritic gneiss, a fine-grained 

 gneiss in the south-west corner of the town, an area of granite or granitic 

 gneiss north of Quincy station, and a band of granitic gneiss north of 

 Rattlesnake mountain, the rocks are mica schists or micaceous gneiss, 

 and they contain either fibrolite or andalusite; the coarse granitic veins 

 carry beryl. Graphite (black lead) is found in the drift north-west of the 

 saw-mill near G. L. Merrill's, and probably came from these rocks. The 

 high bluff of rocks west of the village, and the hills north of West Rum- 

 ney, are andalusite schists ; they are found south of the river ; but the 

 rock of Hawks mountain resembles more the common White Mountain 

 gneiss. In general, the distinction between the rocks of Rumney, and 

 the Montalban rocks as they occur in the White Mountains and east in 

 Campton, is very slight. The andalusite schists consist chiefly of quartz, 

 mica, and fibrolite, or andalusite. The mica is in smaller plates, and feld- 

 spar, except in the granitic veins, is not so common. In regard to the 

 porphyritic gneiss, it is to be noted that in Rumney the band that en- 

 ters the town from the north disappears beneath the fibrolite schists. 



In Groton, in the north part of the town, except in the extreme western 

 part, the rock is entirely fibrolite and andalusite schists. As we go south 

 it divides, and one band goes south-east and extends into Hebron, where 

 it is the rock of the ridge of Tenney hill and Crosby mountain ; it out- 

 crops on the road north of Newfound lake, and here we find some quite 

 good crystals of andalusite. The other band goes south-west, towards 



