C. H. Hitchcock-—Helderberg Rocks in New Hampshire. 473 
nearly white quartz, from 50 to 150 feet thick. This estimate 
came from measurements on the county map for the hypothe- 
nuse, and the average dips afforded data for the two acute an- 
gles of the triangle. The results underestimate rather than 
exaggerate. Another member, seeming to lie at the summit of 
the Lisbon group, but not occurring on this section, resembles 
diabase. This is found sparingly in the very southeast corner 
of Lyman, adjoining the southern gneissic area in North Lisbon, 
and more abundantly directly in contact with the Helderberg 
group in Littleton. Indeed Professor Dana thinks it may be a 
member of the fossiliferous series.* In Lancaster this member 
has its maximum development, and I have formerly mistaken 
It for gneiss, because of the great amount of feldspar present. 
The range of it at North Lisbon will prove specially interesting. 
This group probably crops out in the south part of Littleton. 
Before my last observations, I had supposed the connection be- 
tween the chlorite rock of Littleton and the Lisbon develop- 
ment was well established, but the great abundance of gravel, 
sand and loam renders it difficult to discover any connection 
at the surface. But no doubt can prevent the belief of the 
direct continuation of the Lisbon group into Bath, Wells River 
village and Newbury, Vermont, and so on down the Connecticut 
to Charlestown. 
The western range is more extensive. It abounds in copper 
schists along Gardner’s Mountain, between Lyman and Monroe : 
ut it is not necessary to describe the western range in this 
communication. 
Sipe is a conglomerate of pure quartz pebbles, rarely distorted 
v 
sition. I have spent much time in tracing out its curves, 
breaks and throws, so as to illustrate the forces that have 
operated to derange the New Hampshire formations. 
Along the Lisbon section, the whitish quartzite has a thick- 
ness of only 200 feet, because of a down-throw. When the 
Whole thickness is present, it must amount to 2,330 feet, and 
that after allowing for a possible fold. 
* This Jour., III, vol. vi, p. 350. 
