200 STRATIGRAPHICAL GEOLOGY. 



brown color, not far from an eighth of an inch in diameter. The mica 

 schist is continuous south below Stratford Hollow, but varying consider- 

 ably in texture. Some of the last outcrops of this rock on the south, 

 where it approaches a hydro-mica schist, have the strike E. and W., but 

 the strata are nearly vertical. The inclination at J. Merriam's is 80° 

 southerly. The railway keeps on the drift and terraces of the valley, and 

 nowhere cuts this rock. We have described these rocks as Huronian, 

 except the schists at Island Pond, which probably belong to the Atlantic 

 series. Rocks similar to those near North Stratford, and containing the 

 same kind of andalusite, are found in Franklin county. Me., adjacent to 

 porphyritic gneiss. 



As we enter Northumberland we come to an entirely different class of 

 rocks, that extend along the railway nearly to the tov/n of Stark. They 

 consist chiefly of chloritic feldspathic gneisses, and chloritic siliceous 

 schists ; but on the eastern border the rock is more an argillaceous sand- 

 stone schist. Southward, hornblende and epidote are frequent constitu- 

 ents of this rock. At Groveton there are many outcrops that show some 

 of its different phases, and here, included in them, there is an iron ore, 

 which, with the rock, forms a breccia. The strata in the vicinity of the 

 notch have a north and south strike, are nearly vertical, and are arranged 

 in a series of folds. At Groveton we see the pointed summits of the por- 

 phyrite mountains. The most marked of these is Mt. Lyon. Although 

 the railway nowhere cuts it, yet the high ridge immediately south of the 

 railway in Stark is composed of this rock. It has a dark, compact feld- 

 spathic base, with crystals of feldspar, probably triclinic. Northward the 

 Percy peaks are peculiar in their dome-shaped summit, not so flat as 

 ordinary granite, neither are they as sharp as the mountains of porphyrite. 

 The explanation is found in the constituents of the rocks. Crystalline 

 feldspar very largely predominates ; there is some black mica, and a very 

 small proportion of hornblende. The feldspar does not so readily decom- 

 pose as that of the coarse granite to the north, but resembles that of Mill 

 mountain. In the west part of Stark, on a hill between the railway and 

 the river, we have a granite unlike that found elsewhere. It resembles 

 the Conway granite and the coarse varieties found in Columbia, but it dif- 

 crs in being more compact, of finer texture, and having a feldspar more 

 decidedly flesh-colored. Its proximity to the railway, and the scarcity of 



