Raftsman's journal. [volume] (Clearfield, Pa.) 1854-1948, 1858-10-13
PuYsIcALHIsToR OF THE EARTH
BY PROFESSOR AGAssIz.

1t is something to be able to snow by mon |
umental evidence, and by direct comparison,
that animals and plants have undergone no !
change for a poriod of about five thousand !
years This result has had the greatest infiu- |
encc upon the progress of science, especially
with reference to the consequences to be drawn
from the occurrence in the series OF geologl- |
cal formations of organized beings as highly
diversified in each epoch as those OF the pres
ent dav: it has laid the foundation for the
conviction, now universal among weli-inform-
ed naturaiists, that this globe has been in ex-
istence for innumerable ages, and that the
length of time elapsed since 1t first became
inhabited cannot be counted IN years. Even
the length of the period to which we belong
is still problem, Notwithstanding the precis-
ion with which certain cystems of chronology
would fix the creation of man. There are,
however, many circumstances which SHOW
that the animals now living have been ioE
much longer period inhabitants oi our globe
than is generally supposed. 1t has been posi-
BILE 10 trace the formation and q iowth OF our
coral reefs, especially in Florida, with sufficient
precision 10 ascertain that it must take about
eight thousand years for one of those coral
wallsto rise from its foundation to the Level OF
the surface of the ocean. There are, around
the southernmost extremity Of FLORIDA alone,
four such reefs concentric with one another,
which can be shown to have grown up, one
after the other. This gives for the beginning
of these reefs an age OF over thirty thousand
wears; and yet The corals by which they were
all built mp are the same Identical species IN
all of them These facts, then, furnish as di-
rect evidence aS We can obtain In any Dranch
of physical inquiry, that some, at least, OF the
species of animals now existing, have been in
existence over thirty thousand years, and
have not undergone the slightest change du-
ring the whole of that period. And yet these
four conccntric reefs are only the most DIS
tinct of that region; others, less extensively
*N~ Nnrtl nrI.
indeed the whole peninsula OF Florida con-
sists altogether of coral reefs annexed to one
another in the course of time, and containing
only fragments of corals and shells, &c, iden-
tical with those now living upon that coast.
Now if width of five miles Is fair average
for coral reef growing under the clrcum-
stances under which the concentric reefs OF
Florida are seen now to follow one another,
and this regular succession should extend on
" as far north as Lake Ogeechobee, for two
degrees of latitude. this would give about two
hundred thousand years for the period OF
time which was necessary for that part OF the
| peninsula of Florida which lies south of Lake
! Ogeechobee to rise to its present southern ex
! tent above the level of the sea, and during
which no changes have taken place in the
character of the animals of the Gulf of Mexico.
To form adequate ideas of the great physi-
cal changes the surface of our globe has un-
| derrone, and the frequency OF these modihca-
tions of the character of the earths surface,
| and of their coincidence with the changes OBJ
| served among the organized beings, 1t is ne
| cessary to study attentively the works OF Ellie
| de Beaumont. He, for the first time, attempt
! ed to determine the relative age of the differ
/ ent systems of mountains, and showed first,
! also that the physical disturbances OCCASION
| ed by their upheaval, coiucided with the sue
cessivc disappearance of entire faunG, and
| the reappearances of new ones. In his ear
! Her papers he recognized seven, then twelve,
! aftcrward fifteen such great COMMISSIONS OF
the globe and now he has traced, more or
| less fully and conclusvely, the evidence that
! the number of there disturbances has been, at
| least sixty. perhaps ore hundred. But while
| the genesis and genealogy OF our mountain
| systems were thus illustrated, palseontologists,
| extending .her comparisons between the los
sils of different formations more carefully to
| ali the successive beds of each great era, have
| observed more and more marked differences
| between them and satisfied themselves that
! faun1 also have been more frequently rcnoya-
ted than was formerly supposed so that the
general results of geology proper, and of pal
| poRtolOgy concur, in the main, to prove, that
| while the globe has been, at repeated inter
vals and indeed frequently, though after I'M
n,enselv long periods. altered and altered a.
gain. until it has assumed its present condi-
! ton so have also animals and plants, living
upon its surface, been again and again eXtln-
guishcd and replaced by others. until those
| now Twins; called into existence with
man at their head The investigation is not
in every case sufficiently complete to show
everywhere u coincidence between this reno
vation of animals and plants, and the great
physical revolutions which have altered the
general aspect Of the globe, but it is already
extensive enough to exhibit frequent syn
chronism and correlation, and to warrant the
expectation that it will, in the end, lead to
complete demo nstration of their mutual de
randance not as cause and effect, but as step:
in the same progressive development of th'
a plan which embraces the physical, as well a
the organic world.
In order not to msapprehend the facts, anC
perhaps to fall back upon the idea that thes
changes may be the cause of the difference
observed between the fossils of different pc
riods. 1t must be we'll understood that, while
organized beings exhibit through all geologi
cal formations a regular order of succession
the character of which will be more fully IL
! lustrated hereafter, this succession has been
from time to time, violently interrupted b,
physical disturbances, without any of thes
, altering, in any way, the progressive charac
ter of that succession OF organized beings
Truly this shows that the important, the lead
| ing feature of this whole drama in the deyel
{ opment of life, and that the material worlt
: affords only the elements for its realization
The simultaneous disappearance of entir
fauna, and the following simultaneous appear
ance OF other faun9 consist of the creates
variety of types, in all formations, combines
everywhere into natural associations Of ami
] mails and plants, between which there hav
) been definite relation ar all times, their origi
can at no time be owing to the limited infiu
: ence of monotonous physical causes, eve
$ acting in the same way. Here, again, tn
; Intervention of Creator is display ed in tn
f. most striking manner, IN every stage of tn
history OF the world.