470 STRATIGRAPHICAL GEOLOGY. 



north through Marlow, a mile and three quarters above the village. 

 There are ledges near the road, and it is almost the only rock on the road 

 from C. D. Symonds's to Ashuelot pond in Washington. It is the rock 

 of Huntley mountain, south of Sand pond, and it is probably continuous 

 to Bald mountain, and this appears to be its south-eastern limit. The 

 rock north-west of the porphyritic gneiss is mica schist, containing im- 

 perfect crystals of andalusite ; on the south-east and south we have gneiss, 

 at first fine-grained, but coarse as we go southward. 



Going southward, the next area of porphyritic gneiss is included in 

 the towns of Chesterfield, Swanzey, Winchester, and Hinsdale. This 

 area is wholly in the topographical district we are describing. It forms 

 the high, rough, and rugged portions of the towns where it is found. Its 

 northern limit is about a mile and a half south of Spofford lake in Ches- 

 terfield. It soon widens and sends off an outlier into Swanzey. It ex- 

 tends south into Winchester, and has its southern limit about three and 

 a half miles from the state line. As a whole, the area is oval in shape, 

 and in a line east and west it extends from near Kilburn pond in Win- 

 chester to within a mile of the Ashuelot river. The road from Chester- 

 field to Winchester, except for the first mile, passes over a country where 

 this is the underlying rock. On the road from Chesterfield to Ashuelot 

 village, there are many outcrops. Near its northern limit, not far from 

 D. L. Sanderson's, there are many ledges ; and on the road near Crouch's 

 saw-mill, in the south-east part of Chesterfield, there are numerous out- 

 crops. In Swanzey, near H. Albee's, is a porphyritic gneiss; and here 

 it has a fibrolitic schist interstratified with it, but in a way that seems 

 to show that the schist is the newer rock. Some of the boulders of por- 

 phyritic gneiss here contain fibrolite, which has not been seen in this 

 rock elsewhere. This band of gneiss extends north to school-house No. 

 6, and as far south, at least, as the road that runs past M. Riley's. It is 

 possible that this band may be separated from the rock west, in Chester- 

 field, by a band of schist. Where the porphyritic gneiss is found on the 

 road directly west of Winchester village, the crystals of feldspar are 

 flesh-colored, — a characteristic that is not common in this rock. Where 

 the Ashuelot river has cut a deep, broad ravine through this rock, the 

 stream is rough and rapid ; and as the many boulders with which the 

 channel is lined resist the current, and the water is poured over and 



