Sacramento daily record-union. [volume] (Sacramento [Calif.]) 1875-1891, 1882-04-01
THE 1NrERroa OF THE EARTH.

Various theories have been from time to
time advanced as to the interior condition
of the globe, many of them of purely
fanciful character. The great astronomer
Kepler, for instance, in seeking to account
for the ebb and flow of the ocean tides,
depicted the earth as living monster, the
earth animal, whose whale-like mode of
breathing ocoasioned the rise and fall of
the ocean in recurring periods of sleeping
and waking dependent on solar time. He
even, in his fights of fancy, attributed to
this earth animal the possession of soul
having the faculties of memory and imagl-
nation. Another great astronomer, Hal
ley, was opposed to the idea of the globe
being solid, regarding it as more worthy
of the Creator that the earth, like house
of several stories, should be inhabited both
without and within" For light, too, in
the hollow sphere, he thought provision
might In some measure be contrived. So
recently, indeed, as within the last $50
years, equally singular notions have
been entertained regarding the earth 8
interior. Sir John Leslie, like HALEY,
conceived the nucleus of the world to be a
hollow sphere, but thought it filled, not
with inhabitants, but with an assumed
imponderable matter, having an enormous
force of expansion" Other scientists by
degrees peopled this hollow sphere with
plants and animals-two small subterra.
mean planets, named Pluto and Proserpine
being supposed to shed over this central
world their dim and mysterious light.
Others supposed that the central air was
rendered self luminous by compression, and
hence the two planets were not required.
A certain Captain Symmes, who lived in
the present century, was strongly convinced
of the truth of Leslie's theory. He held
that near the north pole, whence the polar
light emanates, was an enormous opening,
through which descent might be made
into the hollow sphere, and sent frequent
and pressing invitations to A. Won Hum
boldt and Sir Humphrey Davy to undertake
this subterranean expedition But these
imaginative conceptions must one and all
be set aside, and the subject treated on
more prosaic though not less interesting
lines.
The first question, then, that occurs to
one who thinks of the character of the
earth's interior is What is the weight of
the earth-is it comparatively light or com.
paratively heavy? This question has been
answered and though the answers given,
as the results of separate and Independent
forms of experiment, are not all precisely
alike, yet they SO closely approximate to
each other that they may be said to consti-
tute among them something like an author
itative reply. The density of the earth is
found to be as nearly as possible five and a
half times as great as that of water-that
is, our globe is equal in weight to five and
half globes of the same size composed of
water. But. as the average or mean
density of the rocks composing the crust
Of the earth is only two and half
times greater than that of water, it must
follow that the layers of material of which
the mass of the earth's unknown interior is
composed must be of much greater density
than the rocks at the surface. Moreover,
that density may be supposed to increase
by compression the nearer we approach
the center. Were the internal mater.
ais of the same nature as those at
the surface, they would at the depth of a
few miles, be so ompressed-supposing
such extent of compression possible-as to
give much greater density to the whole
mass than the ascertained facts will admit
of. For instance, it has been calculated
that water at the depth of 362 miles
would be as heavy as quicksilver. Now,
this metal at the surface of the earth is
fourteen times heavier than water there
fore, water at the depth of 362 miles
would be rendered by compression four.
teen times more dense than in its normal
condition. Following the same line of cal
culation, marble would, at the center Of
the earth, be ll9 times more dense that it
is at the surface. Professor Judd, how.
ever, in his recent work OF Volcanoes"
expresses the opinion that the ascribing of
such almost unlimited eompressibility to
solid substances can be supported neither
by experiment nor by analogy as various
considerations point to the probability that
solid bodies yield to pressure up to Ger.
tain limit and no farther and that when
this limit is reached an increase in pressure
is no longer attended with reduction in
b llk.
1t was in view of the difficulties which
attended this enormous compression of the
ordinary materials found at the earth's sur.
face that physicists had recourse to the
theory that the interior OF the globe was a
mass of molten matter surrounded by a
solid crust. This theory commended itself
to Fourier and Humboldt and, after their
time, had come to be accepted almost as an
ascertained truth. Among other argu-
ments advanced in support of the theory
was the fact, of which there cannot be
doubt, that high temperature exists in
the earth's crust at some depth from the
surface. The borings that have been made
aud the shafts sunk in connection with
mining operations prove that more or less
regular increase of temperature takes place
as we penetrate downward, the average
rate of increase being about one degree
Fahrenheit for every fifty or sixty fest in
depth, although the rate of increase varies
very much as between different localities.
From the data thus obtained, Professor
Judd has calculated that, supposing the
heat to go on increasing in the above ratio,
there will be found, at depth of 5000
feet, temperature of 2l2' Fahrenheit
sufficient to boil water at the earth's sur.
face while at depth of twenty-eight
miles the temperature will be high enough
to melt cast iron, and at thirty-four miles
to fuse platinum Chambers Journal.