The star. (Reynoldsville, Pa.) 1892-1946, 1892-11-09
AGE OF THE EARTH.
A FASCINATING STUDY THAT IS ELU-
CIDATlNG A GREAT MYSTERY.

100000 and 6so,ooo,OOO Ycars-How
These Computations Are Made.
At the recent meeting of the British
association discourse was delivered by
the president, Sir Archibald GerlSie, on
one of the most interesting problems in
modern science-the age of the world.
Over a century has elapsed since James
Hutton wrote his Theory of the Earth"
which was the first attempt to formulate
chronology of creation in accordance
with the discoveries of science; since
then knowledge has made vast strides,
and his followers have access to n mass
of information which he did not possess.
Playfair and Kelvin improved upon his
work, and now Gerkie and the school to
which he belongs have gone beyond
them.
Biologists have ascertained that the
rate at which erosion takes place can be
measured; by applying their scale TO the
sedimentary rocks they have formed
hypothesis as to the time which has
elapsed since erosion began. To put the
proposition in similar language, the sur
face of the globe is constantly wearing
away under the influence of water and
wind. The portions which are worn off
are carried down to the sea or into hol-
lows, where they are deposited and form
sedimentary rocks. If we can ascertain
how long it takes to form sedimentary
rocl we can figure out when the progress
of wearing away and redepositing began.
Sir Archibald states that on reason
able computation the stratitied rocks at
tain an average thickness of 100, 900 feet.
The material of which they consist was
all washed down from high planes, de-
posted and left to stratify. BY the in
spection of river banks it is found that
in places the surface of the land which
has been carried down as sediment in
rivers has been reduced at the rate of
foot in 730 years, while in other places,
where the land was more stubborn or
less flexible, it has taken $500 years to
lower the surface one foot. The deposit
must be equal to the denudation. Thus
we find that while some of the sedimen-
tary rocks have grown a foot in 730
years others have taken $500 years to
rise that height. Thus the period of
time that was required to build up 100,-
600 feet of sedimentary rock has varied
according to locality from $4,000, 900
years to 6S0,000, 900 years. 1t follows
that the active work of creation lasted
for cycle intermediate between these
two figures. The cycle varied with end
less succession of periods of disturbance
by volcanic force and glacial action,
and the frequent submersion of dry
land, alternating with the emerging of
continents out Of the seas. These may
have retarded the growth of sedimen-
tary rocks, but they cannot have accel-
Grated it.
A study of fossils teaches the steady
uniformity with which the work of
creation proceeded. Since man began
to observe there has been no change in
the forms of animal and vegetable life.
A few species have disappeared one
new species has been evolved. Not only
do we find the fauna and flora of ancient
Egypt as depicted on monuments which
are probably 5000 or 10000 years old
identical with those which are found in
that country today, but shells which in
habited our seas before the ice age and
grew in an ocean whose bed overlay the
Rocky mountains are precisely the same
species that are found in the Bay of
Monterey and the waters of the Chesa-
peake. 1t is evident that there has been
no essential change in the conditions Of
life since these animals and these vege-
tables were first created, yet how vast
the shortest period which we can assign
to the gap that divides us from that re-
mote epoch!
Little by little the geologist is lifting
the veil which covers the prehistoric
record of our planet. The era which
preceded the age of civilized man, with
its vast rivers carrying down diluvial
floods to the ocean, and the bursting
forth OF mountain ranges from contrac-
tions of the earth's crust has been painted
to the life. But no one has exercised his
pencil on that preceding age, when the
forests made way for clumps of stunted
birch and willow, incessant snowfalls
covered the plains, glaciers crept down
from the north, and gradually a vast
sheet of ice half mile thick drove man.
kind, with the mammoth and the rein
deer, to those fortunate regions which,
like California, escaped the agony of the
last ice age.
Nor have we any distinct perception
of that subsequent age when the ice
melted or receded to the pole, or dense
tropical jungle grew up in the morasses
1t had left, swamps steaming with trop-
ical heat swarmed with uncouth ba-
trachian and reptile life, trees of mon
strous growth shed their shade over
shiny pools and black ooze, and in the
distance long mountain ranges whose
fontanel had not yet closed, poured
never ceasing flood Of lava down their
sides. This is page of history which
is yet to be written, but the materials
are accommodating, and the historian will
not be long wanting.--San Francisco
Call.