490 STRATIGRAPHICAL GEOLOGY. 



most northern outcrop where this rock is seen is on Mt. Prospect, in 

 Holderness, and here it is associated with a porphyritic rock, which in 

 some respects is unhke the porphyritic gneiss found elsewhere. It 

 extends southward, and is the rock at Ashland village ; also of Squam 

 mountain to the east. 



On the road north of Little Squam lake, near the town-house, we have 

 the ferruginous schist, and with it the characteristic porphyritic gneiss ; 

 while south, on the road to Center Harbor, particularly at Mrs. T. 

 Shepard's, we have distinct White Mountain gneiss. Elsewhere along 

 this road, northward, the rock frequently contains mica, and is de- 

 cidedly ferruginous, showing plainly that the ferruginous schist and the 

 White Mountain schists belong to the same series of rocks. We have 

 the same change in the rock, though not so marked, going west from Ply- 

 mouth. South, through Bridgewater, the rocks are uniformly pyritif- 

 erous. If this is the same rock as the fibrolite schist or gneiss, then we 

 have a line of outcrops from Mt. Prospect to the southern border of the 

 state, including Ragged, Kearsarge, and Monadnock mountains. In the 

 town of Goshen, east of L. Baker's, we have porphyritic gneiss, and with 

 it there is White Mountain gneiss. East of this is the pyritiferous schist, 

 which here contains graphite. North-west of Washington Centre there 

 are outcrops of this siliceous pyritiferous schist; but it is in Cheshire 

 county where these schists are most extensively developed. They occupy 

 a large part of Sullivan, Nelson, Roxbury, Harrisville, Dublin, and 

 Rindge, also parts of Marlborough, Jaffrey, Fitzwilliam, and Richmond. 

 In Marlow there is a gneissic rock that does not come under either 

 of the heads we have mentioned, and it may form a transition state 

 into mica schist. There are boulders of it at the village, and an out- 

 crop just east, where it is a fine-grained gneiss, and contains a gray 

 fibrolite that has a fibro-lamellar texture. A mile below the village, and 

 east of the road, there are many outcrops of gneiss. Here it contains 

 nodular masses of quartz, from half an inch to three or four inches in 

 diameter; and sometimes it contains amorphous masses of feldspar from 

 half an inch to two inches in diameter. Elsewhere we find the crystals 

 of the common varieties of porphyritic gneiss. Through the west part 

 of Stoddard the rock is gneiss, and is exceedingly variable. On Stoddard 

 heights it resembles a micaceous gneiss. Along the Ashuelot in Gilsum, 



