DESCRIPTION OF THE GENERAL SECTIONS. 653 



through Newbury and Topsham in Vermont, a total distance of eighty 

 miles. 



The Maine portion of this section is believed to consist entirely of 

 Montalban strata, extending to the east base of Pequawket, where it dips 

 westerly at a small angle beneath the mountain. The mountain itself 

 presents interesting peculiarities, whose details are fully given on page 

 237. We find three kinds of igneous rocks, — a sheet of Conway granite 

 at the base, Albany granite in the middle, and the peculiar breccia of 

 Pequawket constituting the upper half of the mountain. From the Saco 

 valley across to the Pemigewasset nearly all the ledges are of varieties of 

 granite distinctly eruptive. At first is the Conway rock ; then the Al- 

 bany granite over the ridge around which the Saco finds it necessary to 

 flow northerly, or the north-eastern spur of Moat mountain. In Upper 

 Bartlett the Conway granite returns, extending about to the west edge 

 of the town. The section just touches the north edge of the Chocorua 

 group in two places, as piled up in the area of Mt. Tremont and its asso- 

 ciated summits. This lies upon a Montalban area in the Saco and Saw- 

 yer's rivers valleys, where the strata show monoclinal Vv^esterly dips. After 

 crossing a little more Conway granite, the section reaches the very inter- 

 esting outlier of porphyritic gneiss in Sawyer's River valley, at the south 

 base of Mt. Carrigain, the most northern exposure of this range known. 

 The relations of this rock to the porphyry of Mt. Carrigain are well shown 

 in Fig. 15, Plate X, save that the gneiss should be represented as dipping 

 east instead of west. The porphyritic area is followed by a broad expanse 

 of Conway granite, capped by the Albany in the upper part of the Han- 

 cock Branch valley, and about the forks of the east branch of the Pemi- 

 gewasset. Near Pollard's in Lincoln, and constituting the west border 

 of the eruptive area, is situated the Conway rock, probably the same with 

 some large eruptive dykes. Between Pollard's and the Pemigewasset 

 river the Montalban crops out with high easterly dips, which are evi- 

 dently normally synclinal. The following broad band of porphyritic 

 gneiss through Woodstock and Benton has not been much studied. It 

 is believed to underlie Moosilauke, so that both the floor and the mica 

 schist of the summit exhibit the basin structure. West of this mountain 

 are the Lake and Bethlehem gneisses, with several folds. In Haverhill 

 the Coos quartzite and schists are well developed, and are fully illustrated 



