492 STRATIGRAPHICAL GEOLOGY. 



studying these forms. The Pinnacle, north-west of the church, is topped 

 out with a coarse granite containing graphic granite and plumose mica. 

 On the south of the Pinnacle and on Bassett hill we have the rock com- 

 mon to this part of the town. In the west part of the town the ferrugi- 

 nous schist appears to verge into the schists and gneisses of the White 

 Mountain series ; at least, there is no well-marked line of demarcation be- 

 tween them, except when we come to granitic gneiss, which is not found 

 with the former. In Marlborough, except for a short distance on the 

 road south-west of Cummings pond, the gneiss on the road west of Stone 

 pond, and in the south-east part of the town, the rocks are either fibro- 

 lite schists or White Mountain gneisses. In the west part of Harrisville 

 the rocks are nearly everywhere pyritiferous. At West Harrisville the 

 cleavage is more distinct than is common in this rock. A mile to the 

 east, where the rock is more gneissic, the strata are bent and contorted, — 

 something not very common in this section. There is a small area of 

 dark gneiss near the outlet of Breed pond. On the road from West Har- 

 risville, and at James Derby's, the rock is also gneissic. To the east, at 

 John Yadley's, the rock is very much jointed and decidedly ferruginous; 

 but east, near S. Follett's, and on the hill south, near J. White's, the rock 

 is less ferruginous, and has somewhat the character of hydro-mica schist. 

 At Harrisville village the rock is gneissic, and resembles somewhat that 

 in Marlborough village. A line drawn from near the outlet of Long 

 pond to the inlet of North pond, and extended southward to the east 

 end of Monadnock lake, would show the eastern limit of the ferruginous 

 schist. 



In Dublin, near P. Morse's, and north-west, we have the ferruginous 

 concretionary schist. On a farm road running south from the road west 

 of Thomas Fisk's, the concretions are numerous and distinct. These 

 schists extend north-west, probably, to the line of Marlborough ; but on the 

 road south from J, Morse's to Marlborough the rock has more the character 

 of gneiss. Near S. P. Frost's, at school-house No. 3, there are numerous 

 ledges. Just north of Thorndike pond, in the south part of the town, is 

 the only other locality where there are characteristic rocks of the ferru- 

 ginous and concretionary schists. Most of the rocks in Dublin, includ- 

 ing Beech hill, the great ridge of Monadnock, and quite an area to the 

 south-east of the village, differ quite widely from these, and will be 



