380 STRATIGRAPHICAL GEOLOGY. 



The three constituents are about equally developed. The general effect 

 of the stone is like that of the Concord variety, only the mica is blacker 

 and more abundant. It is extensively quarried. Its period of eruption 

 must be set down as subsequent to the deposition of the Coos slates, 

 since the latter have been disturbed by its protrusion ; yet the direc- 

 tion of the dip is unchanged, as at J. Blaisdell's in Piermont, dipping 70° 

 N. 50° W. The Haverhill Corner (court-house) village lies on a hill of 

 drift, and hence the junction of the Coos and Huronian systems is not 

 exposed ; but, by following up the valley of the Oliverian stream, one can 

 see much of the structure. At the bridge in the village the rock is the 

 argillitic Huronian quartzite, dipping east and S. 65° E., and continuing 

 for a quarter of a mile up the brook. The Coos schists commence near 

 D. Randall's, dipping 70° west. It slightly resembles hornblende when 

 water-worn, decomposing readily. Higher up the Oliverian, the strike 

 changes to east of north. At P. P. Bowen's the dip is west. There are 

 several good exposures of these schists on the railroad between Haver- 

 hill and East Haverhill stations. 



The order of rocks down Eastman's brook in Piermont has been care- 

 fully ascertained. As before (Fig. 48), we start with quartzite, staurolite 

 schist, hornblende, and the first whetstone slate dipping 70° W. at the 

 junction of the roads from Piermont and Haverhill villages. Then we 

 have hornblende, whetstone, with dip 65° W., and hornblende with strike 

 N. 30° E., vertical. On the hill south the next layer is a small band of 

 quartzite, with whetstone slate, dipping 60° N. 80° W. Then comes an- 

 other small quartzite layer. Between A. C. Walker's and H. Chandler's 

 there is a synclinal of argillaceous schist or slate, the dips being 70° N. 

 60° W. and 80° S. 55° E. This is related to the slates occurring north- 

 westerly at A. W. Putnam's, just in the edge of Haverhill. The rest of 

 the rock to the village of Piermont is mostly mica schist, with and with- 

 out staurolite. Our observations are 54° N. 50° W., 50° N. 60° W; horn- 

 blende band, ss"' N. 20° W., 35° N. 60° W., 45° N. 55° W., and 45° N. 60° 

 W. at the village. Just to the south of the river is a noticeable conical 

 hill, called "Peaked," whose composition is the prevailing rock of the 

 country. It is not easy to comprehend why this conical mass should 

 have been spared, while the adjoining strata were eroded. Similar cases, 

 however, occur in the towns south. First, we have Sunday mountain in 



