New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1874-08-19
PHYSICAL HISTORY OF NEW-HAMPSfIIRE.
BY PROF. C. III. HITCHCOCK.

The physical history of New Hampshire sig
miles sketch OF the growth Of its territory from the
earliest times when 1t was an archipelago Of islands
down 10 the present moment. The subject is novel
oue nobody having studied the history OF country In
that way heretofore The region tho theater OF
Gcting theories among geologists accept the theory
the great antiquity OF the rocks OF the State but
do not discuss e reasons for 1t at present.
The first great period characterized by the forma-
ton OF pOrphyrc granite. the largest ranges OF which
occupied the watershed between the Connecticut and
MerIimac Rivers. The crystals OF felspar very
coarse and usually arranged without order. There
were 20 islands OF this rock at the close OF the first great
peod the most hern lying at the sonth edge Of the
White Mountains This period is supposed to have been
the equivalent Of the Laa g ,i.o, %, u,,o
of Atlantic Group was proposed nearly forty years
tain series to this formation and that
now in a restricted sense The Atlantic consists
NJ three divisions These gneisses I'LL up spaces
tween the several islands OF porphyrlc gneiss. The
Mount Washington range OF mountains Is composed OF
recent Of these and seems to have been elevated
The next great period is termed the Labrador or
Iabradorian period 1t IL the peculiar all that
are here considered, and l can find no descriptions IN
any geological work Of similar structure. The rocks
and are composed Of GRANTEES and compact feldspars
There to have been photographic basin, with
vest Black Mountain in Sandwich upon the south This
basin was filled with overflow OF granite to the depth
of LOCO feet aud 400 square miles After the
solldation Of this liquid granite, it covered by
another flow OF different mineral character. The fist
was coarse reddish granite, the second was deficient
in qnarz Some portions OF this covered by
A third eruption OF granite, best seen on Mount Choir
nina These GRANTEES, in turn, covered by thick
deposits OF clay which altered into compact fespar
both Labradorite and orthocase These several LAYERS
are now essentially horizontal but streams have
oft valleys in the midst Of the plateau and left many
isolated mountains. 800
The Typographical features are to be compared with
those OF Western Virginia where deep ravines have
been excavated Of horizontal plateau This struc-
ture before been Observed because the coun-
try Is entirely away from roads, and covered with the
primeva forest. The State next received aceessiops
along the Connecticut River Valley particularly In the
upper portions. The formation Is termed Huronian,
ana Is Of very great thickness.
The next period is the most extensive OF any. The
rocks consist OF varieties OF mica Scht which Is abund
ant along the Connecticut Valley and the shore The
formation in conformabiy rocks OF tue Atlantic
PERIOD The last period exhibited on the map shows the
area submerged by the In the Heidelberg period
1t occupied principally the Connecticut Valley to the
depth OF 1000 feet
Prof. Hitchcock's paper was illustrated by means OF
an admirable series OF maps showing the growth OF the
State Of coOrs aud called out many express
sIons Of applause.