6lO STRATIGRAPHICAL GEOLOGY. 



clinic feldspar. From the south end there extend large dykes crossing 

 Beaver pond, which are entirely composed of trachyte. This same rock 

 has been discovered by Mr. Hawes in Albany, since the printing of Chap- 

 ter III. It is a very interesting discovery, showing that what has usually 

 been regarded as a volcanic rock of tertiary age has also been erupted 

 in a much older period, and especially in the very ancient region of the 

 White Mountains. The rock will be fully described in Volume III. 



I understand, from Mr. Huntington's statements, that the Montalban 

 rocks prevail through Parsonsfield, Cornish, and Limington with a south- 

 east dip. In Newfield, I found the same rocks abundant all through the 

 western part of the town. The granitic beds are the ones most usually 

 showing themselves. At the Davis mine, close by Balch pond, the dip 

 is high to the south-east, and probably elsewhere throughout the town. 

 Dr. Jackson describes sienite from "Thyng's mountain," without naming 

 the town where it belongs. None of the maps give any such name. He 

 speaks of it as the highest summit in the neighborhood ; and I have used 

 my judgment in locating it in the northern part of Shapleigh, near some 

 houses marked as owned by men having the same designation. I have 

 extended the area of Lake gneiss into Parsonsfield, because the peculiar 

 minerals of the Amherst and Wakefield limestone occur there in two or 

 three localities. When the exact place of this older gneiss is ascertained 

 beyond Parsonsfield, we may have the data afforded for tracing out the 

 master anticlinal of this region. 



I have marked with more care the rocks from Acton across to Bidde- 

 ford. At first are the Rockingham schists, with north-west dip. There 

 is a small anticlinal by school-house No. 6, and north-west dips beyond. 

 Passing through South Acton village is a band of the Kearsarge andalu- 

 site rock, more conspicuous both to the north and south. Half a mile to 

 the east it dips io° W. The south-east part of the town is believed to 

 belong to the Lake gneiss. Very ferruginous rocks appear in Shapleigh, 

 about Emery's mills and at Spring Vale, in which an anticlinal structure 

 may be perceived. After this, we find compact feldspar and sienite in 

 Sanford and Alfred, All through Lyman is an ordinary granite, suc- 

 ceeded at Goodwin's mills by the Merrimack group. In Biddeford is a 

 very beautiful variety of the Conway granite, eruptive, and extensively 

 used for building purposes. 



