New-York daily tribune. [volume] (New-York [N.Y.]) 1842-1866, 1851-04-03

1851.
miles broad, inters pened with a rock resembling,
but which 10 not exactly, gDeiss, in which there
appears 70 be substituted for mica dark colored
lamellar hornblende These rocks are found
more abundsntly in and appear to constitute But
terhill and the DunderbeTg.
But on either side Of the mountains, AT the
Termination OF the hornblende, sort Of transition
areillite commences, and alternstes with transl
ton limettone and grauwacke. In this instance
there are to be found ia the grauwacke consider
able quantities OF terebrAtnlites aud othOcerltes
According 10 minute survey oil this portion OF the
district il is found that all the locks either In the
primitive or transition ranges, incline from YER
tical position toward the northwest The layers
Of granite which are principally embraced by the
gneiss, are composed of half transparent quartz,
very much resembling in appearance hyaline
also silver colored mica, with quite a large pro
portion Of grayish white feldspar, OF peary
iustre The feldspar is lesh colored In come IN
stances although II is not found in this condition
only in limited localities. In some rocksthe field
spar assumes q sky blue color, and the quartz,
sometimes, is ceedibgy dark. Ii is an sscer-
tanned fact that the mica Of the gneiss is almost
invariably Of a dark color, and the fedspar IS
white.
Near Fort Putnam there are extensive beds in
the sness rock consisting almost entirely OF horn.
blenoe and, in the vicinity, too, are also found
crystals Of green augite, though imperiectly de-
veloped. and considerable quantities. Of the
variety Of cocoite consisting OF light greenish
color. Whence the gneiss comes in contact with
the bornblende strata in the bets, there are many
interesting minerals disseminated aud, some OF
the most beautiful specimens OF serpentine IN
calc spar have been discovered IN this Junction,
q short distance north OF the Military Academy,
that the eye ever rested upon-they appear IKE
deep gre en- gems empearled.
The transition rocks Of this district and those
which bound the Highlands on the north ana
south. resemble, in a remarkable degree, the
range of similar formation which skirts the
foot of the Green Mountains OF Vermont and
Massachusetts. But the prevailing rock over
Manhattan Island Westchester, Putnam, and
part of Duchess counties, is gnelss. STU this
rock slternates nth belts of granular limestone,
which seem to extend from Sunderland IN Yer
mont, through Dover Valley, In Duchess county,
scross Putnam aud Westchester counties, to the
Hudson River at Sing Sing and Kingsbridge. and
which affords very valuable qaarrles OF marble
So large has be- the amount Of stone taken
from quarries of this marble in the Dover siley,
that it has required from eight to ten mills KEPT
constantly at work 10 cut il into slabs The most
beautiful materials for architectural ornaments
in this country, is wrought from the quarries near
Sing Sing. In Westchester county there have
been other quArries of the same stone opened by
were taken a large portion ofthe materials which
compose the Custom House in the city OF New
York. At Kingabridge the marble is fall OF iron
pyrites, which, on becoming exposed to the
weather, stain it, and hasten ito decomposition.
The most celebrated and plentiful minerals in
this district glimmer, tourmalines, rough
and crystalized, sometimes black, and at Others
green, red garnets of friable texture, beryle
chaledony steatte. stellated asbestos embedding
crystaized actinoite, blended with serpentlne
and which may be cut into beautiful slabs The
most magnificent usters are blended IN this rock,
representing vegetable forms in painting Amian.
thus is also found here to a considerable extent,
the fbres of which are frequently foot in length,
resembling the appearance of fax. The Southern
part of Long Island is alldvial; bat, In conse'
duence of the country being considered OF the
nature Of the first rock IN place we have incladed
it ntirely in the Southern primitive district. The
spine or ridge OF this Island, and the rocks at what
is termed "Hell. Gate on the Eastriver, and like
wise those found in many places on the Sound,
partske of the primitive character, which eads us
to believe that the Island has been separated from
the main land, by some volcanic or internal con-
vulsion The localities Of Long and Staten Islands,
together with their historical "reminiscences, are OF
a very interesting character and, we may de!-
cribe them more particularly in future communi'
cation. D. W. D.