GEOLOGY OF THE MERRIMACK DISTRICT. 563 



between these masses save in the color. Both sets of joints occur here, 

 as in the regular Concord granite. Of the minor features of interest, I 

 observed a good case of slickcnsidcs, where one part has slid over another, 

 affording a smoothed plane of contact, and small veins of translucent 

 quartz. Ledges of gneiss are found farther south-west, dipping S. 40° E. 

 There is a porphyritic mica schist with gneiss at the crossing of the 

 Nashua river, in the south-east corner of Hollis. The extreme north-east 

 and south-west limits of this area are unknown, on account of the great 

 profusion of sand and gravel in the Nashua and Merrimack valleys. 



3. MONTALBAN SeRIES. 



There are three principal areas of the Montalban rocks in the Merri- 

 mack district, and certainly three smaller patches. The three larger ones 

 are disposed like basins. The first lies in the Pemigewasset valley, com- 

 mencing in Lincoln in the White Mountain district, and extending south 

 to Salisbury. It is connected with our second area, extending from 

 Boscawen to Winnipiseogee lake ; but that is spoken of separately, on 

 account of its great divergence from the first. The third is the largest of 

 all, extending from the west corner of Barnstead south-westerly to the 

 edge of Goffstown and Weare. It is twenty-five miles long and nine 

 miles wide, oval in shape. There is a small area of this rock in Antrim, 

 and a little known expanse in New Ipswich. There is a third in Warner 

 and Webster. 



The Pemigewasset area. This is fifty-five miles long. It starts on 

 the east flank of Mt. Kinsman, increases in width to the north part of 

 Thornton, and then suddenly doubles in size, being divided into two 

 parts by a narrow range of porphyritic gneiss, which keeps close to 

 the Pemigewasset river as far as Campton. The range is eleven miles 

 wide in Campton. It narrows at Ashland to four miles, being covered 

 up by the fibrolite variety of mica schist, possibly a member of the Mont- 

 alban series, carrying the gigantic veins of granite. The same width is 

 attained that we saw in Campton after passing the fibrolite schist. This 

 is continuous to Hill, where the narrowing, on account of the northward 

 extension of the Kearsarge andalusite group, and the westward hedg- 

 ing of the Sanbornton schists, amounts to three and two tenths miles. 

 From Franklin there is a broad spur, extending to the south-west into 



