284 STRATIGRAPHICAL GEOLOGY. 



the crossing of the formation by the Swift Water series. There seems 

 to be a thick mass of schists and conglomerates crossing transversely 

 over the Lisbon series, in a different direction from that of the clay 

 slates just mentioned. It is difficult to understand the precise relations 

 of these rocks without further study. The green schists crojD out on the 

 opposite side of the last-named group at several places, as at the bridge 

 over the river where the railroad bends to the east, overlying the limited 

 outcrop of the Bethlehem gneiss. 



There is a band of hornblende rock commonly separating the Huro- 

 nian from the Helderbcrg. Between Streeter pond and North Lisbon it 

 barely touches the Helderberg, but is a peculiar rock. It consists of an 

 aggregation of radiated crystals of diallage, with a finer paste, com- 

 posed largely of pyroxene. At the saw-mill, about a mile and a quarter 

 south of North Lisbon, it is an ordinary fine-grained hornblende rock. 

 This can be traced on the north-west side of the Helderberg into Little- 

 ton, cropping out at several places, particularly between D. E. Corey's 

 and the river near the line. At very low water it may be seen in the 

 Ammonoosuc, a mile into Littleton. It is next seen occupying the sum- 

 mit of Fitch hill, forming the ridge for half a mile. It is here a compact, 

 massive hornblende, with no indications of divisional planes traversing it. 

 I have thought these several outcrops may represent one geological hori- 

 zon ; and that it is associated with the feldspar and chlorite aggregate or 

 protogene gneiss, which is better developed in Lancaster. It seems to 

 cap the Lisbon group of schists. The dip just above North Lisbon, at 

 the South Branch, is 50° N. 20° W.; near the saw-mill it is 75° N. 50° 

 W.; about the same near the town line ; and probably vertical upon 

 Fitch hill, with a strike of N. 70° E. There is more of it at the very 

 south corner of Lyman, near the line of lenticular quartz beds. 



In the south corner of Lyman the protogene rock (upper member) dips 

 35° N. 30° W. The rock bears a resemblance to elvan, and is more 

 compact here than usual. Half a mile above the ridge, in middle Lisbon, 

 there are hydro-micaceous schists, with a high north-westerly dip. At 

 S. K. Chase's there is a greenish conglomerate, with reticulated veins and 

 pyrites, dipping 60*^ N. 50° W. The band is about a mile in width here. 

 The clay slates join this group at Perch pond, the green schists on the 

 east side dipping SS^^N. 35°W. I cannot find evidence to connect 



