The record-union., 1897-03-30
THE EARTH'S INTERIOR.
Determinations of the Scientists That
the Globe is Solid to the Core.

Until very recent years the fact had
hardly been questioned that by far the
greater part of the earth's interior was
in the condition of a fluid or molten
mass. the volcanic manifestatio ex
hibited on the surface, the rapid rise
Of temperature that is found as we pro-
ceed from the exterior to the interior,
and other considerations pointing al
most irresistibly to such conclusion.
Indeed a common belief was that all
that was solid centered in a crust of
some fifty to one hundred miles
thickness floating" on the fiery magma
of the interior 1t is true that some
physicists, as Hopkins, had reasoned
out a probability that this crust, to
withstand the strains that We're i'm
posed upon it, could not have a thick
ness of much less than 800 or 1,0OO
miles but his arguments had compara-
lively little effect towards dispening the
notions that had SO long existed. AT
the present time, after the brilliant
mathematical expositions Of Sir Will
lam Thomson dord Kelvin), of Pro-
fessor George Darwin, of Professor ST.
mon Newcomb, and Of Mr.. RudSki, this
doctrine of terrestrial fiuidity is hardly
longer taught. few there are who
yet linger with the old theory, but the
great mass of educators and their pu-
pils-except in regions where text
books bear the impress of manufacture
in the mental power of a quarter of
century ago or more-have settled
down to the comfortable conviction
that our planet is as solid or rigid as
a. ball of glass or steel-in fact, twice
as rigid, according to the determination
Of NJ Rudski The doctrine of sOlidity
does not. however, involve the assump-
tion of equal, but of average, rigidty
Again. it is not implied that because
the earth is virtually solid to the core
local areas of liquidMy or fluidity do
not exist. 1t is upon these pockets
or areas of molten material theoretical
ly assumed to exist, that the geologlst
largely relies to harmonize his facts
concerning earth movements, etc.
with those of the mathematical phys
icist; they are to the entire mass of
earth what the air spaces are to
block Of ice Assuming the virtual So
lidity of the earth, the interesting ques-
ton suggests itself: What is the ma
ture of the rock masses that compose
the interior? An answer to this cues
ton is largely one of inference only.
We know the rocks of the exterior,
and we know the rocks of the interior
TO a limited depth. Can our knowledge
OF these rocks be made to answer the
inquiry as to the nature of the rocks
of the deep interior?
1t is, perhaps, too early to give reply
to this inquiry, but the interesting fact
has long been known that the average
density of the earth is nearly or quite
double that of ordinary rock, such as
limestone. sandstone or granite, and 1t
is assumed that its greatest density
cannot easily be less than from five to
ten times that OF its superficial mate
rials or twenty times the density of
water This being so, the rocks of
the interior are either compressed to
prodigious degree to give them this
weight or they are of a different char
acter from those of the surface, possi-
bly, containing great quantities Of met
AL In relation to this inquiry knowl-
edge of the exact density of the earth