HOOSAC MOUNTAIN. 93 



which the observations are platted. In the previous descriptions the Ver- 

 iiiout quartzite had been followed to where the lower part passed into schist- 

 ose quartzite and finally into banded white gneiss, and had been traced 

 down to Dry brook. The upper layer of quartzite also is carried down to 

 Dry brook and appears in massive ledg-es along the brook, just where it 

 issues from the mountain. It is quarried here in a sand mine and runs up 

 the brook several hundred feet in great ledges, striking north 35° west, dip 

 northeast 25°. In one place, a few feet west of the sand mine, the quartzite 

 forms an iron breccia, which is evidence of crushing. From the sand quarry 

 this quartzite can be traced along the strike for a quarter of a mile into 

 the region of. the gneiss. At first it forms a massive quartzite in bluffs; 

 then bands of micaceous gneiss come in; and there are alternating layers a 

 foot or two wide of pure quartzite and layers of finely banded white gneiss. 

 These changes are well shown in this distance. The transition from quartz- 

 ite to gneiss is unmistakable and plainly to be followed. There are ledges 

 of rock here which have elongated pebbles resembling the conglomerate. 

 For a mile north we have a series of fine-grained, banded white gneisses, 

 with steady strike north 40° to 50° west and northerly dip, which on the 

 west slopes of the mountain towards the valley are greatly contorted, the 

 layers of the monocline doubling on themselves and running back in a 

 manner which it would be impossible to describe in detail. 



At a point a mile north of Dry brook, just on the west edge of the 

 mountain, we find a large bluff of gneissoid conglomerate, the flattened 

 pebbles composed of quartz grains, while muscovite and biotite plates and 

 some feldspar, with OCtahedra of magnetite form the cement — a gneiss. 

 The rock is often banded, bands of mica-schist alternating with those of 

 conglomerate. The ledge strikes north 40 west and dips 40° northerly. 

 The continuation of this series of rocks can be traced over a mile southeast 

 with about the same strike and dip. This bluff is on the west crest of the 

 mountain. When we go north from this outcrop we can trace this series 

 of conglomerates within a space of about a quarter of a mile to outcrops 

 with northeast strike and steep northerly dip, then east and west strike with 

 northerly dip, and then the same original strike north 40° west, dip north- 

 east, with which we started; the rock then strikes southeast into the gneiss 



