The evening world., 1890-02-12
WORLDS YET UNFINISHED.
Planets Developing from Gaseous Neb.
uls 10 Solid Earth.
Sir Robert Balls Papers on the
Practical study Of Astronomy.
tCopyyiaht 1900
ny SIR ROBERT BALL.

but the mercst glnnce Mt the SKY through
n telescope will show us that our world Is
only one Of many worlds. Further re.
Fiction and study OF other parts of the
universe will convince us that among
these other worlds there are many in diff.
ferent stages. 30 to speak, Of their devel.
opment.
We may represent our earth. for in.
stance, as a world IN tho maturity of it's
being, but there arc Others which exhibit
different phases of progress. Some will
appear az worlds which aro to be regarded
in extreme old age. while others again
seem TO be in an imperfect or immature
condition. II is of these latter worlds
that we are specially going 20 speak in
this paper.
Suppose that you came into q room and
find a pitcher OF water on the table; you
place your hand on the pitcher and you
feel that the water is tepid. II you knew
that the pitcher had stood there for nm
hour you would be able to draw the con-
clusion that the water must have been
hotter when IL was placed there than
when you felt 1t. II. when vou had felt
the temperature you found the water az
cold as the air in the room. then you
could not infer it's original temperature.
II might have been n jug Of cold water,
to begin with, or it might have been
warm and have grown cold. and you
could not toll which. II, however, the
water be in the slightest degree warmer
than the air in the room, then the argu-
ment that II must have cooled from q
higher temperature is irresistible. This
il so obvious n doctrine that IL may seem
unnecessary to write 1t down. But, OBJ
yious though u II be, it will yet teach us
much about the past history both of our
earth aud of other globes: especially will
1t prove instructive aboutthose unfinished
worlds of which we are speaking in this
paper.
IL in n blacksmith's forge You incau-
tiouslv placed your hand upon a piece of
IRON aud it burned your fingers. and IL
the blacksmith told you that the iron had
lain there for half an hour, you would not
doubt that il must have been much hotter
when the blacksmith drew II from the fire
than you have now found it to be. Prob
ably 1t was even red-hot at the time it
was laid aside.
The argument would still apply If the
object. instead of being n lump of iron.
we're a block or stone 1t would apply If
the body were AZ big az n mountain or as
big as the moon; neither the fire nor the
material would really affect the reasoning.
IL you found the body to be heated you
might feel perfectly certain that hours ago,
or years ago, or centuries ago, il must
hnve been hotter still.
We must apply this argument to that
immense globe, 3, 900 miles in diameter,
on which we are standing. 1t has an ex-
| Aar.-. nr.,u nN roaly aV.l tatna A-l ---
tains q good deal of iron inside. This
great ball IL undoubtedly very hot in Its
interior; we have many reasons for know
ing this to be the case. The eruptions of
volcanoes afford the simplest proof. The
smoke. the ashes and the molten lava that
volcanoes pour forth show us that the
earth is anything but cool III the lower
regions.
Other terrestrial phenomena bear SINH
lar Testimony. Hot springs, for instance,
evince the heated condition of the deep
seated rocks. Any miner will tell you
that the deeper his mine the hotter he
finds his work to be. The gain III heat
arises from the fact that the deeper the
mlne the nearer 1t lies TO the central in
candescence.
We are not now referring 20 such heat
as is produced by combustion. We are
discussing the way in which n body which
has one been heated by afre or by some
other agency gradually parts with It's
heat and falls i'll temperature. There III
no means Of replenishing to any large ex-
tent the heat of the inside of our earth by
combustion. The earth's interior temper
ature must therefore. on the whole, be
simply fallingn accordance with the laws
Of cooling.
The conclusion to which we are led BY
this reasoning is n remarkable one. We
know that our earth has been IN existence
for an incalculnble period OF time. We
are not even able to estimate how many
thousands of years have elapsed since man
began his course on our globe, but the
human period is merely the latest Of all
the great periods in world history.
Long before man commenced TO live
here the earth was the abode of lite,
countless races Of animals. large and small
now generally extinct. roamed through
forests OF trees or through vegetation Of u
kind largely If not wholly different from
anything which now grows. Time after
time have these races of organized beings
passed away aud been replaced by Others
entirely different.
There were times when this globe was
inhabited by reptiles far larger than any
terrestrial animals now living. All the
geological gardens IN the world at
present would not be nearly large enough
to contain representative specimens of all
the varieties of animals which have from
time to time found "A home on this earth.
hut these animals have now passed
away and the only means we have of
learning that they ever existed is afforded
by the occasional skeletons that IN the
form of fossils are o and then ex-
tracted from the rocks.
No one has succeeded in making any
reliable estimate OF the number OF years
which have run their course since first
this globe assumed its present shape. But
no one eau doubt that these years are TO
be reckoned IN their millions, though
whether these millions are TO he expressed
in units or tens az hundreds, or in periods
even greater still is a matter beyond our
knowledge.
During all these ages the Garth must
gradually have been growing colder, and
therefore at the tcgInnng II must have
been much hotter than 1t Is to-day. As
We look back earlier and still EARLIER the
earth ever seems hotter and hotter
through the ages. At least the argument
points to a time when the earth must have
been hot even To its surface; so not that
you could not stand on IT and then
earlier still it was red hot, white hot and
molten.
Even here the argument does not fail.
We hnd the heat must have been ever
greater aud greater the further We look
back, until at last We come o. u line
when the nov sold materials of u earth
must have been IN a widely different