coos AND ESSEX DISTRICT. 79 



is of a triclinic variety. At the saw-mill on Phillips brook there is a 

 trap dyke six feet in width. 



In the vicinity of Berlin falls, veins and dykes arc very numerous. 

 The schistose rocks at the village, and just above, along the railway, 

 have been replaced by coarse granitic veins, consisting of vitreous C|uartz, 

 feldspar, and patches of black mica. In the railway cut just below the 

 station there are several trap dykes. In the second cut there is one 

 twenty feet wide, and it is separated from another four feet wide by a 

 band of gneiss a foot in width. The general direction of the dykes is 

 north-east and south-west. In the road just below the village there is 

 an extensive dyke, and at the falls below the bridge one four feet wide 

 extends along the river. It is porphyritic, and its direction is N. 8o° 

 W. Near the falls there is also a granitic vein, containing magnetic 

 iron ore, and it is so mingled with the rocks as to form a metalliferous 

 porphyry. 



In Berlin, on a high bluff north of Dead River pond, there are several 

 veins or beds, the rock of which, though it has the appearance of jasper, 

 is really a compact feldspar, as a partial determination of its constituents 

 shows. It contains silica 69.2, alumina 19.6, lime 3, and its color is 

 greenish brown, striped with bands of reddish brown. The beds vary in 

 thickness from a few inches to several feet. At one point there is Cjuite 

 a cave ; its length is fourteen feet, and it is nine feet in height and six 

 feet wide. On the floor of the cave there is an accumulation of vegetable 

 mould, which contains fragments of the felsite. It has been thought by 

 some that this cave was excavated by the Indians, to obtain the rock for 

 making arrow-heads. The entrance to the cave has somewhat the ap- 

 pearance of having been excavated by human hands ; but, as the vein of 

 felsite at the entrance is not more than a foot in width, and within a 

 few feet of the entrance on the east there are several veins much wider, 

 which appear never to have been touched, that they would have removed 

 a large mass of granite to get this particular vein does not seem proba- 

 ble. The presence of fragments of felsite in the cave similar to those 

 found where felsite is known to have been wrought by the Indians, 

 makes it probable that they visited this cave, and it is possible that they 

 may have enlarged it somewhat ; but the origin of the cave must have 

 been a fissure in the rock. 



