GEOLOGY OF THE MERRIMACK DISTRICT. 479 



of the Stream near Mrs. R. P. Holt's, then runs south nearly parallel with 

 the line of Groton, and strikes the corner of Orange. Included within 

 these lines common gneiss is the only rock, except a feldspar porphyry 

 on the new road east of Norris pond, and a breccia, with porphyry, on 

 the east side of Pollard hill. The dip of the strata here, as in Went- 

 worth, is easterly. 



The gneiss of Canaan has not that uniformity of texture that we find 

 in the gneiss of Dorchester and Wentworth. While the protogene gneiss 

 in the west part of Canaan is coarser than that northward, the other 

 gneisses become finer-grained and more variable in texture ; besides, we 

 have hornblende schist that appears, in some instances, to be interstrati- 

 fied with the gneiss. Sometimes these hornblende bands are continuous 

 for some distance. One is seen on Indian river, near East Canaan, con- 

 tinuing west, parallel with the railroad. It turns north, extends along the 

 west side of the Pinnacle, and northward, crossing the road near J. P. 

 Barber's. That which outcrops near R. Hayward's is probably a con- 

 tinuation of this, and possibly that at R. Atwell's ; — at least, we find that 

 the coarse gneiss which we have in Dorchester and northward, is east of 

 the line of the outcrop of this hornblende schist, and that the rocks 

 intervening between it and the protogene gneiss are generally fine-grained 

 granitic gneisses, and probably form the upper division of the Bethlehem 

 group. These rocks extend south, and occupy a large part of Enfield ; 

 for directly south from Canaan the Bethlehem gneiss disappears, and it is 

 only in the extreme east part of Enfield that the common or Lake gneiss 

 is found. These fine-grained granitic gneisses in the north part of Gran- 

 tham are replaced by the Lake gneiss. It is difficult to tell anything 

 about the stratigraphical relations of this granitic gneiss, since the ar- 

 rangement of the constituents of the rock gives little or no indication of 

 stratification. In Canaan, on the west, we have the Bethlehem gneiss ; 

 but south, in Enfield, we have argillaceous schists, mica schists, and 

 quartzites. The line that separates the schists from the granitic gneiss 

 runs — from a point half or three quarters of a mile east of the north- 

 west corner of the town — south-east; but after it passes Lily ponds it 

 turns a little to the west, then suddenly to the east, and forms a curve 

 around the Lake gneiss in the north part of Grantham. As a whole, this 

 area of granitic gneiss is oblong. It is about twelve miles in length, and 



