566 ©. H. Hitchcock—Helderberg Rocks in New Hampshire. 
next the Ammonoosuc River, and, with the mica and horn- 
blende schists, is perhaps our Swift Water series. The horn- 
T 
“Bethlehem gneiss,” or rather the common variety upon its 
border. The mica is black, and the feidspar often scanty. 
The position differs from that of the other rocks. Its norm 
position is about 40° dip toward the north, both the inclination 
and course varying from those of the other strata that have 
been cite : 
This section, if protracted, would cross another interesting 
Helderberg area; but for the sake of clearness, I will add a 
small section (fig. 9) with greater horizontal scale, situated about 
a quarter of a mile to the southwest, crossing the Ammonoosuc 
nearly at North Lisbon railroad station and passing up its 
“south branch.” The gneiss dips 36°, N. 85° W. at the “ Lead 
mine.” Next is a coarse conglomerate, seen in the field and 
under the bridge, 3 65°-70, N. 10° W. As there is a 
oO". N. 10° W. | They are traversed by beautiful ribbons. of 
banded trap from half an inch to three inches in width, which . 
- 
ing essentially the same strike and dip with the last mentioned 
