The Savannah morning news. (Savannah, Ga.) 1900-current, 1902-06-07
STATE OBJ EARTH's INTERIOR.
Sir Robert $. Ball on Earthquakes
and Their Causes.

ana
In Sir Robert Stawel Balls THE
Earth's Beginning" published by D.
Appleton & Co., the writer says:
high temperature must be found at
the depth of even a small fraction of
the earth's radius, and the excessively
high pressure characteristic of the
earth's interior must be borne in mind
in any consideration of the condition of
the matter there found. If we were to
judge merely from the temperatures
| reasonably believed to exist at a depth
of some twenty miles, and if we might
overlook the question of pressure, we
should certainly say that the earth's
| interior must be in a fluid state. It
seems at least certain that the temper
atures to be found at depths of two
score miles, and still more at greater
depths, must be so high that the most
refractory solids, whether metals or
minerals, would at once yield if we
could subject them to such tempera-
lures in our laboratories. At such tenn
peratures every metal would become
| fluid, even If it were not transformed
| into cloud of vapor But none of our
| laboratory experiments can tell us
whether, under the pressure of thous-
ands of tons to the square inch, the
application of any heat whateverd
would be adequate to transform solids
into liquids. 1t may, indeed, be reason
ably doubted whether the terms solids
and liquids are applicable, in the sense
in whcih we understand them, to the
materials forming the interior of the
earth.
If a solid can be made to behave Ike
! a liquid, even with such pressures as
are within our control, how are we to
suppose that the solids would behave
with such pressures as those to which
they are subjected in the interior of the
earth? The fact is that the terms
solid and liquid, at least as we under
stand them, appear to have no physical
meaning with regard to bodies subject
led to these stupendous pressures, and
this must be carefully borne in mind
when we are discussing the nature of
the interior of the earth.
1t must, however, be admitted that
the interior of the earth in its actual
physical state seems to possess at least
one of the most important character
| isticS of a solid, for ii seems to he
| intensely rigid. We mean by this that
the material of the earth, or rather
each particle of that material. is very
little inclined to move from it's position
with reference to the adjacent particles
by the application of force. Possibly
| a liquid, such as water, might not
behave very differently in this respect
from a solid such as cast iron. if each
of them were exposed to a pressure
of scores of thousands of tons per
| square inch, as are the materials
which form the great bulk of the earth
But, without specializing on these
points, we are able to demonstra te
that the earth, as a whole, does ex-
hibit extreme rigidity. This is one of
the most remarkable discoveries which
has ever been made with regard to
the physics of our earth. The discov-
cry that the earth is so rigid is mainly
due to Lord Kelvin.
The same writer says that there is
much difference of opinion as to the
causes of earthquakes. He says:
But it will not be doubted that an
earthquake is one of the consequences
| though perhaps a remote one, of the
gradual loss of internal heat from the
earth. AS this terrestrial 1 eat is
gradually declining, it follows from the
law that we have already so often had
occasion to use that the bulk of the
earth must be shrinking. No doubt
! the diminution in the earth's dame
ter due to the loss of heat, must be
excessively small, even in a long pc
| riod of time. The cause, however is
! continually in operation, and, accord
! ingly the crust of the earth has. from
| time to time, to be accommodated to
the fact that the whole globe is les
SEEMING The circumference of our
| earth at the equator must be grad
ually declining, a certain length in that
circumference is lost each year We
may admit that loss to be a quantity
| far too small to be measured by any
observations as yet obtainable, but
nevertheless. it is productive of phe-
nomena so important that it cannot be
overlooked.
1t follows from these considerations
that the rocks which form the earth $
crust over the surface of the continents
and the islands, or beneath the beds of
ocean, must have a lessening acreage
year by year. These rocks must, there
fore, submit to compression. either
continuously or from time to time
and the necessary yielding of the rocks
will in general take place in those re-
| gions where the materials of the earth 8
| crust happen to have comparatively
small powers of resistance. The acts
| of compression will often. and per-
| haps generally. not proceed with uni
/ formity, but rather with small sue
cessive shifts, and. even though the
/ disbursements of the rocks In these
shifts be actually very small. yet the
pressures TO which the rocks are sub
| tected are so vast that a small shift
may correspond TO a great terrestrial
disturbance,
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