24 STRATIGRAPHICAL GEOLOGY. 



strata of the same name in New Hampshire, Vermont, and Canada, overlying the 

 Huronian. The latter may merge into the andalusite variety cropping out on Mts. 

 Monadnock, Kearsarge, the east side of Washington, etc. 



In the south part of Lunenburg the section crosses an interesting band of white 

 quartzite over fifty feet wide. This band I have traced directly to Nottingham, N. H., 

 the rocks becoming more micaceous and schistose north of the state line. Lithologi- 

 cally, it closely resembles two bands of the same rock crossed farther north by our line. 

 The outcrop is on the track of the Fitchburg Railroad. 



The section next crosses a broad belt of gneiss supposed to belong to the Atlantic 

 system, and to consist mostly of the Lake division. Four well marked anticlinals have 

 a place in it before coming to Monadnock. The first is the Wachusett anticlinal, fig- 

 ured by my father in his final report, and not observed on the line of section, perhaps 

 for lack of outcrops. As it occurs on both sides, it must be continuous across the sec- 

 tion, while there is evidence to suggest the erosion of its eastern portion. Mt. Wachu- 

 sett lies on the eastern flank of this axis. The next anticlinal makes the dividing ridge 

 between the Merrimack and Connecticut waters in Ashby, Mass., and New Ipswich, 

 N. H. The fourth axis brings up the underlying porphyritic gneiss. Between the 

 main water-shed and Monadnock is the stratigraphical place for two remarkable bands 

 of white quartz. These have been described and mapped in the annual report for 1873. 

 As their outcrops have been traced almost continuously from Temple and Mason to 

 AUenstown, if not Strafford, no doubt can remain as to their persistency. A protracted 

 search has so far been unavailing to bring them to light in New Ipswich, most of 

 Mason, Rindge, or Sharon, but two similar bands appear in Royalston, Mass., along 

 the same north-east-south-west line ; — so that the theory is admissible that the nearly 

 horizontal mica schists of New Ipswich, Ashby, and Temple may conceal the under- 

 lying quartzes for a considerable distance. The same bands come up again between 

 Keene and Connecticut river. 



Mt. Monadnock seems to be an isolated contorted synclinal of andalusite mica 

 schist, resting upon the upturned edges of the gneisses. The vicinity of the mountain 

 is a plateau (Vol. I, p. 209), so that these schists suggest an incredible amount of ero- 

 sion. The little map in this chapter shows the extension northwardly of a series of 

 these outliers. 



The Montalban division makes its appearance between Monadnock and Keene.* At 

 Troy village the dips are easterly, so that the older rocks beneath Monadnock are ar- 

 ranged in synclinal form, showing that the andalusite schists were deposited along an 

 original depression. The "Concord granite" of Marlborough succeeds, with essentially 

 the same position. 



Near Factory Village, in the north-cast part of Swanzey, the Lake division of the 

 Atlantic group makes its appearance, and continues to the newer rocks of the Connect- 

 icut valley. In the south part of Keene the dips conform to the overlying Montalban 



* The facts stated concerning the strata between Monadnock and Connecticut river are furnished by J. H. 

 Huntington, from recent field-work. 



