176 STRATIGRAPIIICAL GEOLOGY. 



the ridge the slate runs back on to the south slope of Mt. Field. There 

 is a gradual slope north-easterly from the base of the formation at the 

 south of Mt. Willey to a point on the railroad 2000 feet south of Willey 

 brook. From Mt. Webster this dividing line between the granite and 

 slates is very conspicuous, the former rock being bare and white, and the 

 latter black and obscured by bushes. The general course of this forma- 

 tion from the Willey summit to its extreme northern development, a little 

 north of Willey brook, is about N. 10° E. 



The sudden falling off of the mountain south of Willey has been no- 

 ticed. It is due apparently to the disappearance of the slate, the broad 

 terrace-like hills beyond being composed of the underlying granite. 

 The slates stop suddenly, cut off as abruptly as the end of a plank. 

 They do not seem to have been altered into anything else, but have been 

 removed bodily. In character they are identical with the rock at Willey 

 brook, and in the valley running north-westerly from that point. I ob- 

 served no andalusite in it, but cannot doubt it exists as abundantly on 

 Mt. Willey as farther north. 



A very interesting feature is displayed at the lower limit of this 

 formation, on the head waters of Kedron. The Conway granite there 

 approaches it, but between them is a harder variety of granite, accom- 

 panied with fragments of slate imbedded in it. The Conway rock is 

 surely the cementing material of the harder bunches with the slates. 

 This agrees with what has been described on the stream above Beecher's 

 cascades : in that, pieces of this newer slate have been cemented into a 

 brecciated mass by the Conway granite. 



On the Portland & Ogdensburg Railroad these slates are exposed for a 

 width of 2700 feet, 700 north of Willey brook. Their usual inclina- 

 tion both south and north of the brook is 6"]° N. 82° E., with a reversed 

 dip a few rods north along the railroad. On top of Mt. Willard the dip 

 is north-westerly ; and on the way down the mountain I have noticed 

 the presence of an anticlinal of small extent near the line of junction. 

 The deep cut just south of the iron bridge over Willey brook has a 

 smooth westerly wall. As the same seam is perceptible down to the bed 

 of the brook, it is likely that a fault is indicated by it, though not one 

 of sufficiently great importance to complicate the structure. The ledges 

 here are beautifully filled with long crystals of andalusite. 



