The herald., 1912-12-12
THE EARTH CRUST
Its Density, Its Thickness and the
Pressure It ExertS.
a BAR TO WORLD EXPLOSION

Volcanic or Gaseous Forces at Work
Could Never Be Blown to Fragments
Some writer's have accounted for III,
asteroids on the theory that they ar,
the fragments Of world that IRON
some unknown cause has been eIpiod
ed in its orbit. Similarly, many have
thought that perhaps at some distant
time, when the seas shall have been
drunk up into the cracked and thick
ened crust of the age shrunken earth
and the yolcanoes-those vents OF tn,
fiery interior-shall have become cho6
ed and extinct, the pentup gases gener
ated from the descending moisture by
the still great internal heat may ac
tually explode the old earth like
veritable bombshell.
But that can never happen.
In 1888 Krakatoa, sleepy old vol
cano on a small island In the strait
of Sunda, between Java and Sumatra,
began to show marked signs Of uneasi.
ness. Round the volcano the quakinG
bottom Of the sea. down which rushed
Niagaras of water. Then the assures
closed and confined the engulfed food
In the hot subterranean depths. The
water was quickly converted into
steam, the steam into ASSOCIATED
gases, without room for expansion.
1t exerted a pressure equal to that
of the strongest dynamite.
The great chimney Of Krakatoa
sealed since the memory Of man
barred the normal path Of escape
Higher and higher mounted the pres
sure under the huge mass OF the vol
cano; then. Of sudden. came a blast
that actually shook the earth. Never
before In historic time had there been
such a shock. The whole top Of the old
mountain was blown into the sky. The
recoil was distinctly felt clear through
the terrestrial ball.
This great cataclysm has been cited
as an indication of the power Of the
pentup forces that may some day dis
rupt the earth itself. Let Us examine
the underlying principles that must
guide US IN passing judgment on the
correctness Of this theory.
An explosive compound Is a combust.
ible combined mechanically or chem
ically either with oxygen or with an
oIidizing substance that will burn with
out the help of atmospheric oxygen.
Among the most powerful high ex,
plosives are nitrogelatin and picric
acid, each Of which has a density more
than one and a half times that Of
water. The products Of their combus.
ton are nearly all gaseous, whereas the
products Of the combustion Of ordinary
black gunpowder are less than half
gaseous The larger part is the solid
matter that makes the smoke
The energy that a high explosive can
exert depends on the volume Of the
gases liberated and the temperature TO
which the heat Of the explosion can
raise them.
The exact temperature Of the gases
liberated by high explosive at the in
slant Of detonati ton Is not absolutely
known. but may be approximately
learned through chemical experiment
Nor is the amount Of pressure known
with absolute certainty. 1t is probable.
however, that nitroglycerin. nitrogela.
tin and picric acid. when detonated in
a confined space. exert a pressure some
where between 100000 aud 100000
pounds to the square inch.
II we assume that the earth crust
has density five times that Of water
and that its average thickness is fifty
miles, then it follows that it exerts a
pressure of more than 100000 pounds
to the square inch; If the crust Is a
hundred miles thick, then the pressure
is more than a million pounds to the
square inch-a pressure certainly great
er than the expansive force exerted by
the most powerful high explosive
Plainly. no quantity of high explosive
detonated under the crust Of the earth
would be able to lift II, and consequent
ly we know that no world of the size
of the earth can ever explode from its
own pentup internal forces.
If. then. no high explosive force is
sufficient to blow up a world the size
of the earth. how can worlds explode?
There is only one way in which the
heavenly bodies can become possessed
Of sufficient energy actually to blow
up. and that is by collision.
The stars are flying about In space
with velocities that range all the way
from five miles second to 500 miles a
second.
II two celestial orbs, travelling each
at velocity of 200 miles a second. met
In head-on collision they would be
fused and gasiied by the impact, and
the heat generated would be sufficient
to break up the matter of both into its
ultimate elements and to expand 1t into
nebulous haze. This is the way in
which Snionca Souc that po,x- .,ns porr