442 STRATIGRAPHICAL GEOLOGY. 



few rods west. These may be spoken of again in the description of the 

 section upon this hill. After protracting these quartzites west of Fall 

 river, upon the map, none of them seem to connect directly with the 

 band east of the stream back of the school-house. 



Little is known of the extension of the Perchog Brook (Winchester) 

 quartzite southward. I have noted it as having a westerly dip near the 

 north line of Northfield. The Massachusetts map represents a range of 

 it reaching to Miller's river, through Northfield and Erving. Starting 

 from the place where it is known to occur in Winchester, at a saw-mill 

 near F. Doolittle's, just in the edge of Winchester (Nos. 90, 91), there 

 is a quartzose conglomerate, carrying a little galena. 



5. Coos Mica Schists. 



We have at least three prominent varieties of these mica schists. 

 I. An ordinary mica schist, argillaceous, and containing crystals of stauro- 

 rolite. 2. Very siliceous mica schist, without staurolite. 3. Even bedded 

 slate, with and without staurolite. In this latter variety, this mica is 

 abundant in small, brown prisms, showing their faces where the strata 

 have been broken. Though resembling phyllite (chloritoid), it is likely 

 the mica is a phlogopite. Small red garnets are often present in great 

 abundance, so that when freshly fractured the surface of these slates is 

 covered with small pimples and pits. We have often, in the field, dis- 

 tinguished between the Coos and Cambrian slates, by observing the 

 presence or absence of these pimples. The distinction is not complete, 

 since the Guilford and Vernon slates are often much pimpled, yet belong 

 to the older series. 



In Hinsdale and Winchester the mica schists carry beds of granite, 

 both coarse and fine grained. Other beds are of nearly pure quartz, of 

 mechanical origin. 



Wantastiquit mountain is mainly composed of these mica schists which 

 are thought to overlie the quartzite range in the north part of Hinsdale, 

 already described. The strata on Bear hill dip easterly at a high angle ; 

 and the position all through the eastern part of Hinsdale is essentially 

 the same. These beds of granite show themselves in climbing Bear hill 

 from the north. Ashuelot river has cut through the ridge at Hinsdale 

 river, but it rises in Foxden mountain to fall again southerly in the south- 



