Harrisburg telegraph. [volume] (Harrisburg, Pa.) 1879-1948, 1919-01-02
TEACHER TELLS
ABOUT FOSSILS
BY Garrett Z. Serviss

very much interested, l went to the
! library. but could find out no more,
so 1 write you. Sarah f.
You pay me a great compliment,
and wish 1 could deserve it, but I.
too. am dependent on teachers and
| books; although everybody, of
course, can add to knowledge by
thinking about it.
Let us think Il little about what
you have been told, and have read,
concerning fossils. They are found
buried and embedded in rocks, and
their appearance shows that they
are the remains and the marks of
animals and plants which were once
alive. How, then, did they get in
and under the rocks?
To answer that question we must
first consider what kinds of rocks
the fossils are found in. Upon eX-
animation we discover that they are
only rocks which have been formed
by the solidication of mud, sand
and such other materials as COL
lect at the bottom of bodies of
water. These are called stratihed
rocks, because they lie in layers
or strata, and can be split up, or
separated, as if they were floors
piled one upon another.
Land and Water Fossils
We conclude that when the ami
mails and plants whose fossil re-
mains and tracks are found in
these rocks, were alive, they must
either have inhabited the water
which then flowed over the places
where the rocks now lie. and have
been buried at its bottom, or they
must have dwelt on land which was
later overflowed by water and COW
cred with deposits of mud and sand.
1t is not difficult to distinguish
I between the fossils of creatures
that. lived in water and those that
| lived on land, and they are often
found intermingled because they
were brought together in certain
! places which were once the shoes
! of lakes and seas now no longer in
existence.
But another question arises: How
! does it happen that fossils are found
in rocks which form hills and noun
tains, far from any sea or lake,
| and at elevations thousands of feet
| above sea-level? To this the reply
/ is that those hills and mountains
! must be composed of rocks whose
/ original state was that of mud and
sand collected in thick deposits at
the bottom of water, that the fossils
! found in them must represent ami
! mails and plants that were buried
! in those deposits, and that at q
I later time some convulsion of the
earth's crust lifted them all up into
| highlands and mountains. Another
/ branch of geology than that which
: deals specially with fossils will tell
| you astonishing facts about the rise
and fall of the lands of the globe,
! the invasions and retreats of seas
and the crumplins and fracturing
] of the earth's mighty shell, as if it
were the surface of a ball of drying
/ clay. But let us stick to the fossils.
! There are half dozen different
sorts of fossils. Some consist OF the
bones or shells, or a portion of the
bones or shells, of ancient animals,
which have been preserved in the
hardened rocks that were mud
banks when the animas were
buried. Others, particularly plant
fossils, are carboniZed remains of
/ the original vegetable forms. Coal
is that kind of fossil. A third sort
! have literally been turned into
/ stone skeletons, since the substance
of the bones of the animals or the
stems of the plants has been re-
placed particle for particle, by min
eral matter which exactly initiates
the original forms.
How Ages Arc Fixed
A fourth kind of fossil consists of
mould of the original animal. the
latter having entirely disappeared,
leaving only a cavity of its own
shape in the hardened rock. This
cavity has sometimes been filled
with other material. Then there
are fossils which like the Siberian
mammoths and the amber-bedded
flies of the Baltic coast, have been
| entirely preserved, not only in form
but in substance. The mammoths
have been cold-storaged, so to
speak, while the flies have been
embalmed. Fossil tracks. of course
! represent only the impressions made
/ by animals walking or crawling
over wet sand or mud on the
beaches of ancient lakes and seas
or the shores of now vanished rivers
and swamps.
BY careful study, and the com.
parison of the same kinds of strata
in different parts of the earth
geologists have been enabled to. as.
sign relative ages to the various
stratified rocks, and thus to fine
out the order in which different
species OF animals have made theil
| appearance in the world The
strata are very much broken up II
consequence of the commissions tha'
the slowly cooling planet has suf.
fered, but yet it is possible to ar.
range them in a progressive order
the deeper ones being the older
while the upper ones are compare.
lively recent.
Names have been given to the
successive periods and ages repre-
sented by the principal statiflca
tions, which may be likened t.
the pages of a book, lying will
it's title page downward. The fos
sils are like pictures on the page!
and the earlier in the geological
book fossil-picture occurs the
moro ancient must be the time tt
which it belongs.