New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1879-08-16
LIFE OF THE SILURIAN AGE.
BY S. w. FORD.

TEE NIAGARA AND SALIVA PERIODS OF THE UPPER
sILURIAN.
"Amid all the revolutions of the globe" says
Io,ovtair in his illustrations of the HuttOnlan
theory. "the economy of nature has been uniforms
md her laws are the only things that have resisted
the general movement. The rivers and the rocks,
.be seas and the continents, have been changed in
ali their parts but the laws which direct those
changes. and the rules to which they subject.
have remained invariably the same"
The facts of Silurian geology are calculated TO
strongly impress the mind with the truth of Play
fa,r,s observations. Looking at the Lower Siluran
5enosits we have in the Primordial period,
olternations of slate-rock, congomerate sandstone
and limestone the whole representing in Eastern
No-tb America a total thickness of 5000 feet or
more in the Canadian period, first sandstone, then
Alternating states and limestOnes. and lastly lime
tome tthe Chazy) the whole reaching in the region
,,o,tioned. n thickness of nearly 5000 feet and
snaIlv in the Trenton period, as | have already
shown in article No T. first limestone, next slate,
and then shale 1.-THE latter meaning splintery or
maven shifting slate)-the whole attaining along
the Appalachians a thickness Of from 1000 to $500
feet These facts abundantly prove that during the
Lower Siluran era the law of physical change was as
oII-Dervading as now. The more prominent changes
that occur in the life of the era have already
snoken Of but il may here be remarked, that there
snDears 10 be no good for suppOsing that the
influence of environment upon organism was at
that time any more potent to effect radical changes
than now.
Rut while the record of Lower Silurian time is
Tins record Of changes on an extensive SCALE 1t is
rome the less true that it furnishes evidence OF IN
tervening periods of repose of enormous DURATION
and Of which we are scarcely able to form any ade-
ouate conception. The Trenton limestone. for in
stance is 600 feet thick in Pennsy wanna ana the
Hudson River shaes are sometimes LOCO feet thick
In New-York The Utica slate has thickness along
the Mohawk Valley Of from 200 to 800 feet. Lime
stone rocks are known 20 increase very slowly, and
since the rate of growth of those now forming Is
prettv well known, we are enabled to form some es-
innate of the probable duration of the Trenton
epocb but no positive conclusions are possible IN
asmuch as a variety Of influences with which we
are unfamiliar may have increased or diminished
the present rate. Bat, at all events. we may
feel assured that there was no for haste or
hurry. The Utica and Hudson River beds lmainly
fine mud-rocks) were also evidently slow IN the
forming and vet number of the fossil species
range through the whole series, or from the lower
beds of the Trenton TO the CHER beds of the Hud-
son River group.
AT the close Of the Trenton period great change
occurred resulting in America, in the almost COM
plete destruction of the living species and, over
wide regions in the uplifting, folding and crystal
Ization of the rocks. The Green Mountain region
at this time became an area of permanent dry land
and thus a part of the existing order
of things The Upper Siluran rocks mostly
thin out toward the region, and evidently
never covered it. 1t is, therefore, one