3l8 STRATIGRAPHICAL GEOLOGY. 



the township. They follow a road parallel to the Ammonoosuc between 

 the South Branch and Salmon Hole brook. Near the South Branch we 

 have in order, proceeding northerly, gneiss, slaty layers, perhaps slightly 

 calcareous, dipping 80° north-westerly, quartzite, with a dip of 75° S. E., 

 limestone, and quartz. This series is only a few rods wide. Quartz and 

 limestone, with gneiss, are found along this road nearly to Salmon Hole 

 brook (near J. Hildreth's) in a very narrow band. The quartzite is evi- 

 dently older than the adjacent staurolite schists, and the structure may 

 be anticlinal. The limestones are connected with the gneiss, being of 

 the same age with the bed at Bronson's kiln. The quartzites are rejDre- 

 sented in the Ammonoosuc collection, in Nos. 2S;^-y88. See, also, the 

 Map, PL XH. 



The Coos area east of the Ammonoosuc naturally divides itself into 

 two parts mineralogically, the western consisting of clay slates, with 

 many garnets and a few staurohtes, and the eastern part being a mica 

 schist, everywhere stauroliferous, and often holding magnificent crys- 

 tals. The slates at the upper end occupy about half the space between 

 the quartzite range and the Huronian, At the south-west end of Streeter 

 pond the dip is N. 27° W. at a high angle. A mile west the position 

 is the same. Near the mouth of the South Branch, at a bend in the 

 stream, these slates dip 60° N. 29° W., and are exposed for a width of 

 thirty rods. The relations of the slates to the adjacent Huronian and 

 Helderberg strata are given further on, in a section under the descrip- 

 tion of the latter rocks. On Salmon Hole brook these slates dip 85° W. 

 The section in Fig. 28 crosses this and the schistose band farther south 

 along Mink brook. The thickness of the clay slates here is given at 

 3000 feet, with an average dip of 58°, and that of the schist at 3300 feet. 

 Beginning at the Atwood gold mine on this section, the following were 

 the dips observed across the slates : 48° N. 62° W., 50° N. 67° W., 64° 

 N. 57° W., 68° N. 62° W., and 65° N. 32° W. The distance is about fif- 

 teen sixteenths of a mile. These slates terminate on the west side of 

 Pond hill in Landaff, with the dip 58° N. 32° W. 



The mica schists begin in the edge of Bethlehem, south of W. Bur- 

 leigh's, on the road from Littleton to Franconia, with the dip 20° N. 

 57° W. The valley continues to Baker's hollow in Bethlehem; and it 

 would not be surprising if the staurolite rock extended further in that 



