HOOSAC MOUNTAIN. 89 



In the Iloosic valley here we have the Stockbridge limestone crossing 

 the valley from the Greylock side and running close up to the slope of the 

 hills on the east side. This limestone is succeeded by a broad band of 

 quartzite (Vermont) on the slopes of the hills and this again by a series of 

 gneisses (Vermont) which extend to the crest and back from it, east. In 

 the southwest part of the map the quartzite occurs in a long ridge running 

 northerly and southerly, just cast of the Hoosic river. It is a very massive 

 vitreous variety, the dip of which is obscure. 'A little hollow, perhaps a hun- 

 dred feet wide, separates it from the gneisses on the east, which strike north 

 25° east parallel to the trend of the quartzite, and dip first west then east — 

 much folded. Following 1 mile north from here without finding out- 

 crops, we come to a creek running into the large pond in the valley a few 

 hundred yards north of Berkshire depot. Just where this creek issues from 

 the sloping benches a little east of the road we find well-marked ledges of 

 the limestone striking north 37° east, dip steep westerly; 125 feet east the 

 next outcrop dips east 65° and is in contact conformably with a calcareous 

 quartzite; for one-half mile or more up this creek beds of this calcareous 

 quartzite are found, in places massive quartzite; then, after a covered inter- 

 val of 400 feet, we find ledges of laminated gneiss (quartzose) dipping also 

 cast 50° (strike north 40° east); farther up the creek this gneiss is succeeded 

 by coarse gneisses with blue quartz resembling the granitoid, also dipping 

 east. We have here a transition of the Stockbridge limestone into the Ver- 

 mont quartzite, and this is in turn overlain by gneisses, the whole series 

 inverted. The limestone is covered along the contact from here north to 

 Cheshire. The line of contact between quartzite and gneiss can be easily 

 followed north along the side of the mountain, the two rocks never quite 

 in contact, until we reach a point on the side of the mountain half a 

 mile south of the north end of the pond; here the quartzite and underly- 

 ing line grained gneiss make a sharp turn, and, as is so often the case in 

 this region, in the turn the rocks are not eroded away. The southernmost 

 outcrop of a laminated quartzite strikes north 45° east, dips 60° west; across 

 a little ravine to the north this curves to strike east and west, dip 50° north- 

 erly. It is overlain by a large bed of very massive vitreous quartzite, and 

 near the outcrops of the latter numerous angular blocks of a quartzite-brec- 

 cia cemented by limonite occur — a rock often found in these sharp turns in 



