GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. 20I 



building-Stone in this part of the state, make it worthy of attention for 

 local, if not for more extended use. This granite, at least along the rail- 

 way, is limited to this hill, for the next outcrop of rock is at Devil's Slide, 

 just west of Stark station. Here we have a variety of rocks. At the 

 west side the rock is a beautiful sienite, but unfortunately it is not easily 

 wrought. Going up the steep ascent, the quartz disappears, and in places, 

 also, the hornblende, so that we have only a crystalline aggregation of 

 feldspar. Half-way up the rock is colored by manganese and other sub- 

 stances, so that it is a dingy mass, mostly feldspar, with a very little 

 hornblende ; and we have included the whole under the general term of 

 porphyrite. The east end of the slide is a dark siliceous schist, that 

 stands vertically by the side of the intrusive porphyrite, but there are 

 places where it is penetrated by it ; and boulders forming a breccia can 

 be seen at the boarding-house near Hickey's mill. 



The mountain opposite, that rises a thousand feet above the station, is 

 composed of essentially the same rocks as the slide ; but on the west side 

 of this mountain, from the base far up its slope, there are boulders of lab- 

 radorite, though diligent search has not revealed a single outcrop. The 

 marvellous beauty of the finely-striated crystals of the feldspar is shown 

 by polarized light in the microscopic sections. The vertical walls of the 

 slide, shown in the heliotype opposite page 69, and Mill mountain, rising 

 so high and shutting by the slide, give to the place a picturesque beauty, 

 especially when the setting sun throws a deep shadow over the face of the 

 slide, and casts across the vast amphitheatre the sombre hue of evening 

 while as yet the mountain is in the bright sunlight. Leaving the station, 

 we pass the limit of the porphyrite, and at Stark water-station we strike a 

 dark siliceous schist. Going east, the rock resembles somewhat a hydro- 

 mica schist, but still it is a gray siliceous schist, and numerous outcrops 

 can be seen. The railway cuts it in the east part of Stark, in the corner 

 of Dummer, and several places for a mile east of West Milan. It has 

 both easterly and westerly dips, but the easterly dips prevail on the west, 

 and the westerly dips on the east, so, as a whole, it seems to be a syn- 

 clinal axis, with minor folds near the middle of the area. These rocks, 

 except the hard siliceous schists on the west, we have placed in the 

 Lyman group, which is the upper member of the Huronian. On the 

 railway, not far from the one hundred and fifth mile-post, we have a 



VOL. II. 26 



