St. Paul daily globe., 1884-10-12
WHY THE EARTH 0UAKEs.
Forces that are Pent ttp under Us and
You'd Smash Us If IYseU Got Loose.

Prof. George II. Merriman of Rutgers
college, New Brunswick, has made the crust
OF the earth study, and has written on the
subject. He says:
while facts enough regarding the extent
of the earthquake of Sunday have not come
to hand to enable me to speak on the direc-
ton OF the earth wave or its peculiar features
as compared with other earthquakes, yet
something may be said as to the latest con-
victions of students of science on the nature
of the earth below the point any man can
penetrate. That may lead us to guess in
telligently at the cause of earthquakes.
"You know the long-received theory of
the nature of the interior of the earth was
that it is a molten mass, and that we move
around on crust enveloping the earth and
caused by the cooling off of this mass on
the outside. 1t is undoubtedly true that
about thirty miles below the earth's surface
the temperature is so high that everything is
in melted condition. We know this be-
cause we have learned that every fifty feet
we penetrate into the earth there is an in
crease of temperature of about one degree,
and at distance of thirty miles the heat is
so great that any substance we know of
would melt. Perhaps the melted mass is IN
the form of liquid. That would be certain
but for the immense pressure on it. The
pressure is estimated at 10000 tons to
square foot. Of course scientific men can
not experiment with matter at high tenn
perature with pressure of 10000 tons to a
square foot, so we can only guess what may
be its condition. In talking about this mel
ted mass thirty miles under US the term
water substance is used by geologists.
''How great is the distance through this
water substance we do not know, but it is
certain that its density increases more and
more gradually until the interior of the
earth is solid, probably, from the incon-
ceivable pressure, 1000, 1000 or 5000 miles
from the surface. Sir William Thompson
has demon strated that the earth must have
a core much denser than the land and water
we live on. He points out the fact that if a
shell only thirty miles thick surrounded a
molten liquid mass, extending from one
side of the earth through the centre to the
other side, then the moon, through the law
of gravitation, would displace the liquid or
gas in the interior of the earth to such an ex-
tent that the earth's crust would bulge out
in the direction of the moon, making tide
in the solid crust of the earth, as certainly
as the skin of au orange bulges out when you
squeeze the fruit between .he palms of your
hands. And this would be evident to us be-
cause the ocean tides would be almost, if not
quite, imperceptible to US. To withstand the
attraction of the moon, the earth, Sir William
says, must be as rigid as steel
$50 we have the theory the crust of the
earth floats on and imposes an immense
weight on water substance which is incon-
ceivably hot. Now, as to the way an earth
quake may be caused. Suppose moisture
trickled gradually, year after year, through
this crust into the heated mass. In our at
mosphere steam would be produced. Thirty
miles below us the pressure is so great that
it is not likely that steam could be genera
ted One thing, though: the pressure of
10000 tons is to the square foot, pressure
exerted in every direction, would be in
creased. Some effects must be produced
down there, and it is easy to see that if one
place in the earth's crust is weaker than
another near where the water trickled in,
then ''the weakest place must STAN the
strain" 1t is not unreasonable to suppose
that this pressure from below, might be so
great that the earth's covering was shifted a
little to adjust itself to the pressure from be-
low. This shifting of the crust is, in fact,
the earthquake.
~ believe this theory has the greater
reason on its side, because earthquakes are
almost always in the region of volcanoes,
and volcanoes are almost always in or near
t.e ocean.
Another theory of earthquakes is that as
the earth is very gradually cooling off the
crust thickening on the other side, and
scracks or assures on the under side of the
crust many miles deep may occur in cou
| sequence of the enormous pressure, so tina
| the water substance rushes into new posi-
ton with a force that woold knock a CONT
nent out of shape if it took place on the
earth's surface. That motion would bt
sufficient to produce vibration thirty miles
distant.
''Whatever the cause of the earthquake OF
Sunday added Professor Merriman, ''
think the earth in the region where it tool
place has either settled into new position
or is forced back into an old position from
which it was pushed by former earth
quakes.-N. y. Sun.