New-York tribune., 1874-11-06
THE DECAY OF CRYSTALLINE ROCKS
Bv Prof 7. Sterry Hunt

Pr0t. hunts auureS3 was uellVeTcu WlJnOuI
manuscript notes lie alluded 10 his previous discus
sions the chemical decomposition Of crystalline sill
Gated rocks and spoke of the evidence that this
had been in operation from before the beginning of
poeozoic time, but had become comparatively insignia,
cant since tho postpliocene glacial erosion lie hai
already maintained that up to that time the hills oil
New-England like those OF tho Blue Ridge further
SOUTH had been deeply covered by the ssus @ OF tatr m
the former region portions OF this material had escaped
d % a mada o hs Il the se case
examination Of the tunnel tnroagn the h3o,aS oaaS
that at its end the tunnel had been
driven for many hundred feet through mass OF
decayed mica slate and gneiss of which the feldsDar
had been turned into cay Tnis change was complete
to depth or 200 feet from the present surface Higher
mn on the western flank the mountain its crest
and eastern sde hard and undecayed rocks OF the same
kind seen, with glaciated surfaces, but the process
OF erosion mad spared the great mass OF sofened and
updlsurbed nearly vertical strata at the western base
OF the mountain. He then proceeded to notice the
Connecticut where according to the observations Of
c. u Shepard long since made, tn brown henati,e iron
OF Salisbury and Kent are associated with WHAT Is
locally called uers earth. bat consists according to
Shepard Of nearly vertical strata OF crystalline strata
decayed 10 place, described at the Hoosac tunnel
Fro comparison Of the Of iron thus found
with the similar observed IN the decayed crystal
line rocks Blue Ridge which were recognized as the
results of the alteration OF beds and Odes OF iron pytes
and in some OF beds of spIthc iron Ore found In
prof Hunt argued that such had been the source OF
much OF the hematte found along the great Appa'
lacan Valley aud related his recent OBSERVATIONS IN
Lehigh County Penn, at the northwest base OF the
South Mountain. where such ores are mined at depth
of 70 feet in vertical of soft caycy matter and
once his opinion, beds OF pYres IN crystalline
Some % 0sSs s 3i tsss Of
Hurouiau, to which lie referred these beds In Lebigh
County. ,.,
by its solution furnished the whole OF the iron ore
or 1c rocks at different horzons From these decayed
strata had the materials for all the cldrOcks
and sand-rocks OF various ages ne 70 ea
the OF organic matters ana prougnt
down 10 '1e zen na or Inv When bos iron ores and ocares
are forming remarkable example OF this pro-
deposited n the Clinton period. after the spreading
great mass OF mechanical sediments OF the
A discussion on this paper followed, IN which Prot. W.
B. Rogers confirmed the speakers views ana
the crystalline rocks. He had also himself observed
that on the east side Of Blue Ridge, Buckingham
composition in place Of pyrtes beds IN the ancient
crystalline. so-caed talcose states Prof James HAL mad
ore in the decayed rock Of the Hoosao
Mountains where 1t was seen both at the outcrop on
the hillside and in the tunnel below DR.. Geuth had
lately the soft, tacke material from one OF
the Pennsylvania hematte beds and found It to be
Lesley discussed The question OF the perodcty OF
naIedaoie series which Dr. Hunt stated to depend In
his opinion the alterations Of level and the changes
in virtue OF which sands ana are 20
DR.. F. v. Hayden, who has just closed his seasons
work OF 10 10y
m the caons leading into Colorado River and upon
the plains IN the vicinity supposed to have been built
more than years ago by the ancestors OF the present
MoQuis Indians full description Of these remarkaoe
ruins has already appeared in THE TRIBUNE In letter
from a member OF tue exploring party. DR.. Hayden
quoted largely from this letter. The Important fact
estabshed by these discoveries s that there once OK
sted In what are arid plains and savage gorges
Of South Eastern Colorado race 80 far cviizea hat
hey built large cies constructing their houses OF we'll
hewn blocks OF stone. with timber floors, welformed
windows and doOrways and smoothly plastered walls
and that they possessed the art OF making glazed po1
teri