The Placer herald., 1867-04-06
THE WONDERS OF GEOL0GY-THE
MYSTERIES ON THE CREATION
LECTURE BY PROF. WILLIAM DENTON, AT CHI
CAOO.

LECTURE BY PROF. WILLIAM DENTON, AT CHI
| CAGO.
Prof VIM. Denton, Of Massachusetts, de,
livered the first Of series Of lectures last
evening, in the music hall Of the opera house,
on the subject Of "Colorado and its mineral
resources" The lecture was delivered to a
large audiance, and being preliminary, it was
on the subject Of general geology.
The lecturer commenced by the state.
ment that biographies were tie most inter-
estng Of books, and Of these aulobiographies
were the best, and be came to present the
autobiography Of our glanet, or TO trace the
history Of the earth from its infancy to the
present time.
The earth was once mass Of fiery matter
10 LIQUID form. The evidence is abundant
and demonstratve that this is so. The in-
crease Of heat as we 90 towards the center
of the earth is evidence Of this; for about
fifty feet the heat Of the earth increases one
degree.
At the depth Of forty miles the heat would
be between 5000 and 1000 degrees. Deep
copper and coal mines, and deep a,tesian
wells show this. Another evidence Of the
interior heat Of the earth is the presence Of
Of hot springs in various parts Of the earth.
The shape Of the globe furnishes evidence Of
its former huidty. The motion Of the earth
upon its own axis has fattened at the poles,
but to allow it TO take this shape it must
have been fluid, and if it was fluid, it was so
because Of its molten condition. Volcanoes
furnish another evidence of the earths inte
rial fuidty. They are the chimnies going
down to the central fires. Volcanoes are
found in all zones and all continents.
The crust Of the earth bears the same pro-
portion to the fluid portion that an egg she'll
does to the interior Of the egg. The ancient
volcanoes are always larger than the recent
ones, and while the active volcanoes are only
two hundred and twenty five in number, the
extinct ones are numbered by thousands
Hence volcanoes in ancient times must have
been more frequent than at present. Earth.
quakes are still another evidence Of in,era
fires. There is an earthquake somewhere on
the surface Of the earth every three days. I'm
agine the condition Of the earth's interior.
Go through sand and lime and clay, 20 the
gnerss, to the mica; till the rocks become
warm; still deeper is the copper, deeper yet
we find tons of pure gold. Deeper, deeper,
and the light begins to dawn, for the rocks
are glowing; still deeper, and you stand on
the shores of the moultern internal sea. 1t
is calm as mirror, yet there are sometimes
storms on that seattle result Of and earth
quake on the surface. It may be that cleo.
tricry causes this agitation, but nothing is
certainly known of its causes. The earth
was once an entire mass of moultern fire. 1t
is incouceivatle how long it has taken to
cool it. Lava moved down the sides Of
Etna nine years after it was elected, aud
lava thrown from Jaruia, in Mexico, 100
years ago, is hot yet. How long, then, must
it have taken 10 cool the earth's surface to
its present telnperature! All the water on
the surface of the earth now was then vapor
or gas, held in the atmosphere. After
time the vapors were condensed to water and
the seas and oceans were formed. Then the
rocks were bare and rugged. Then was the
period of gigantic geysers. At this time the
foundations of the world were laid-the
granite was then crystalized, the granite is
The basis Of all rocks. At this time there
was no life on the globe, and it was long be-
fore life made its appearance. Mountains
were raised, valleys depressed, the rains de.
cended aod wore down the old rocks, and
thus the newer rocks were formed. First
in this series of rocks came the metamorphic
rocks-rocks that are stratifed but yet have
been changed by heat. In this wearing pro
cess alluded to, the quartz in the granite
formed sandstone and quartzite; the mica
formed micaschist; the feldspar formed
slate
After the metamorphic rocks come the
slurian rocks. In these are the first remains
of living things in the shape Of fossils. Some
times the indentical thing is found in pet
rified state, sometimes its least" only; some
times merely the loot.mark of the animal.
Without fossils the history Of the earth
could never have been searched out. They
are the written history of the globe. The
siluran rocks in England are 10000 feet 10
thickness We know that they are Of this
depth by the uplifting or t!lting Of them in
the mountain ranges, where their width or
depth can actually be seen. In this way the
order Of the strata have been observed that
lie even ten miles below the surface. In the
silurian times there were no land animals
and no land plants, except few MOSES that
are found at the surface Of these strata.
Life began in the ocean. 1t began in the
low form Of polypus and fucoids. Then fol-
low shells. Those on mountains and rocks
entirely composed Of shells. The stones used
in tagging the walks Of Chicago belong t., to
the surian period. In this period shells
grew larger than they ever bavs since. Spec
linens Of orthoceratite have been found in
Wisconsin twelve inches in diameter and
twelve feet in length. The first appearance
Of fishes is found in the upper layers Of the
silurian dposit called Ludlow bone beds"
The next layer is called Devonian. This is
mostly composed Of the old red sand stone.
This period has been called the age OF fishes
from the immense number that are found in
it. A ledge Of Dovoniau rocks is to be seen
at Louisville, Ky. 10 this rock is found a
coral that looks like honey-comb; and this