Omaha daily bee., 1900-02-11

state Of izneous huidity; that the mass va.
long kept at about the same temperature boy
q process Of boiling. When the sphere as.
sumed its present state Of approximate so.
lidity lie further cooling would have led 10
the chilling OF the outer part. while the cen
tral portion remained o.. near its original
heat. 4 little reflection will show that. UNI
der these conditions. we should have a rapid
increase OF temperature for perhaps a few
score miles downward. while below a GER
tain level the Increase OF heat would be a.
a steadily diminishing rate-the greater part
OF the internal mass being at q rather uni
form heat.
When the understanding Of the evidence
derived from volcanoes had advanced be-
yond the primitive notion that they were
due to some kind OF subterranean combus-
ton. such as takes place in burning coal
beds, biologists adopted the view that they
proved the interior to be in a fluid state.
substantially like molten glass or iron. II
did not seem possible otherwise 70 account
for the outpouring OF iavas in such quanti-
ties that they have covered to great depths
areas many thousand square miles in ex-
tent.
Further proof to the sane effect seemed
to be afforded by the fact that wherever We
az y NAHNfo w u sSNulllht 4ANhSH Jun a.
granite, which hav; been brought into con-
tact with other deposits, they have entered
fssures in a way that shows that they were
originally fluid. The hypothesis OF internal
fuidity appeared at the beginning Of this
century TO be tolerably well approved; it
was indeed assumed by most writer's and
was made the basis of many learned trea-
tises. Steadily, however, within the last half
century the contributions from other
branches Of science have served 10 bring this
view into doubt. First it was noted that any
melted rock shrinks in general to the
amount OF about 10 per cent Of its bulk in
solidifying, and in consequence of this tends
to sink as it freezes. This tendency to set
tie Town into an interior fluid would make
it possible for the crust Of a generally fluid
earth to attain a greater thickness than
about half a mile before 1t would be dragged
down by gravitation. As we know that the
earth is solid for at least twenty miles
downward, and probably is in that state for
several times that depth, the idea OF a thin
crust lying as a layer on a liquid interior
pas shaken.
The next attack on the notion OF internal
fuidity came from the astronomers. 1t had
long been known that the gravitatiye at
traction OF the moon on the equatorial bulg-
ing Of the earth, or, rather, the difference
in this pull on the parts of that mass near
to and away from our satellite, caused the
polar axis to be constantly changing its
position. The geological bearing of the
movement is found in the fact that, If the
earth were fluid except for its crust, the
position Of the polar axis would not be
altered by the attraction, but the sphere
would change shape in the manner OF g
tide. as the waters do under a similar i'm
pulse. While the problem is complicated
and the results not accepted by all students,
it seems from this argumen most likely
that the earth is as rigid as the most solid
OF its rocks.
GeoIogists' Views Reviewed.
In face of the evidence as to the difficult
ties of reconciling the great heat OF the
interior, and the election or lavas, with the
evidence that shows that it cannot be huid,
biologists OF this century have had TO re-
view many opinions which they inherited
from the last. To begin with, they have
hau to modify their conceptions OF solids
and fluids so as to clear away certain mis-
conceptions due to our experience with ma
terials on the surface Of the earth. The
phrase hard as a rock expresses a hlgh
order of rightly or resistance to strain
wher judged by ordinary conditions such as
we are accustomed to-; yet, when deeply
buried and subjected TO the vast stresses
which are due TO the contraction OF the
mass. from the constant loss OF the internal
heat. rocks creep in the direction of least
pressure, Ike wax. They twist and fold, as
dc sheets OF wet paper; they behave IN a
manner hat we are not accustomed to as
sociate with solidity.
We may see how inadequate are the COM
mon views as to the strength OF materials
bv observing what takes place when an
armor-piercing shot strikes a thick plate OF
steel. such as is used to protest the vital
parts of a battleship. The shield is made or
the most rigid substance that has been con-
triyed. It's resistance is far greater than
that of any rock. Yet, when struck by the
pl oiectile, it yields and is pushed aside as
earth by the plowshare. 1t may splash, as
mud when a pebble is thrown upon it.
The facts above set forth, as well as other
considerations which it is not necessary to
present. have led those biologists OF our
time who are concerned with the difficult
problems OF the earth's interior TO look upon
that realm in a different way from their pre-
decessors of a hundred years ago. 1t is now
generally believed that the temperature in
the depths. though not as great as 1t would
be If the rate Of increase in heat which We
observe in mines continued Onward TO the
center. is still hot in a measure not APP
preached in any furnace, or even in the
electric are. That this heat does not resolve
the matter into vapor, as 1t would like ma
terials on the surface, or even bring it 10
the fluid state. IS explained by the action of
the pressure TO which it is subjected.
Pressure That Would Solidify Air.
We know that pressure tends to consoli-
date all substances. Even the relatively
riding amount of 1t that we can apply By
our arts will llquefy air. II We could expose
this fluid air 10 the weight Of a hundred
miles of everything rock we may fairly pre-
sumo that its particles would be 50 driven
together that il would become in a manner