C. Hl. Hitchcock—Helderberg Rocks in New Hampshire. 567 
stream. The rock is a gritty hydro-mica schist, so far as seen. 
Probably this is the place for a hornblende aggregate or chlor- 
itic rock, which is seen on the west side of Streeter Pond in 
situ, and in enormous bowlders between North Lisbon and the 
pond. These hard rocks terminate just as the stream bends 
and passes through a narrow rocky gorge of clay slates con- 
taining staurolite and garnet, dipping 60° N. 17° W. Th 
ip is manifest higher up. The ledges extend for 25 or 
30 rods, after which the rocks are covered with earth for a 
great distance. The banks are made up of bowlder clay, which 
is undermined by high freshets, and the road has been torn 
away so many times that the town authorities have been com- 
pelled to discontinue the carriage road, thus necessitating 
pedestrian explorations in this interesting spot. A slate similar 
to that just described crops out on the new road from the sta- 
tion to Streeter Pond, about a mile northeasterly. The course 
is nearly east and west, and the strata are more nearly vertical, 
but the ledges must be continuous between these points. It is 
shown also by the presence of enormous blocks of diabase, 
whose source must be to the north of the slates and not far dis- 
tant. The map shows the distribution of all the parts of this 
section. The width of the Helderberg conglomerates is about 
forty rods, which implies a thickness of at least 500 feet. The 
clay slates correspond perfectly to portions of the Coés group 
in the Lyme and Lisbon sections, as well as to the interesting 
staurolite slate seen at Purple’s quarry in Bernardston, Mass., 
described by Professor Dana. . 
North Lisbon Helderberg. 
The rocks of the North Lisbon terrane have been described 
in part, but not the most characteristic ones. About 100 rods 
below D. Richardson’s, on the east bank of the river, are white 
limestones containing fragments of the large crinoids. The 
limestone occurs on both sides of the river. These localities 
are southwest from fig. 9, and the limestone may prove to be 
one or two hundred feet thick. Mr Huntington first found 
these large crinoids, and we traversed the region together the 
last day of our stay in this region. Contiguous to the lime- 
stone is a dark slate, softer than that on Blueberry Hill, which 
must belong to the series. The same may be true of thick 
masses of hornblende rock bordering the Helderberg on the 
northwest flank. | 
Other Helderberg Localities. 
There is no time to describe other localities of the Helderberg 
with detail, I have long been satisfied that Dalton Mountain 
belongs to this series, and we have strong suspicions that some 
Am, Jour. asian” Series, Vou. VII, No. 42.—Junz, 1874. 
