The Mitchell capital. (Mitchell, Dakota [S.D.]) 1879-1918, 1897-05-14
THE EARTH's lNTERlon
Reason for Believing the a.,
= Solid to the Core pe

Solid to the caae Globe Ia
Until very recent years the r,o.
hardly been questioned that by tr f,rA aad
greater part Of the earths intera. Tue
in the condition of a fluid or iva. was
mass, the volcanic manifestationoV' V''ea
hibited and the surface, the rania eS'
of temperature that is found os Use
proceed from the exterior to tho wv. We
ior, and other considerations non.. nes'
almost irresistibly to such conclna.s
Indeed, a common belief was tba, a,'Oa,
that was solid centered in a cru". al!
some to 100miles thickness "aoat;no.. y.
on the fiery magma of the interior ;.
is true that some physicists as d.. %
kins, had reasoned out a nrohoha:
that this crust, to withstand the straias
that were imposed upon it, could ras
have thickness Of much less than ~. -0s
or 1000 miles, but his arguments hoy
comparatively little effect toward div
dispelling the notions that had no lon, mo
existed. At the present time, after tbe
brilliant mathematical expositions .,
Sir William Thomson Iord Kelvin -
Prof. George Darwin, of Prof Sim,
Newcomb and of Mr.. Rudski, this do.
trine of terrestrial fiuidity is barln
longer taught. A few there are wba
yet linger with the old theory. but tba
great mass of educators and their nv
pills in regions where tav,
books bear the impress of manufacturs
in the mental power of a quarter Of
century ago or more-have settloa
down to the comfortable conviction
that out planet is as solid as a ball ~
glass or steel-in fact, twice as ricid
according to the determinations of VI
Rudski. The doctrine of solidty does
not, however, involve the assumntion
Of equal, but of average, rigiditv
Again, it is not implied that becausa
the earth is virtually solid to the core
local areas of liquidity or fluidity do
not exist. 1t is upon these pockets or
areas of molten material, theoretica]lv
assumed to exist, that the geologist
largely relies to harmonic his facts
concerning earth movements, etcl
with those Of the mathematical pbvsi.
cist; they are to the entire mass of the
earth what the air spaces are to block
of ice. Assuming the virtual solidity
Of the earth, the interesting question
suggests itself: What is the nature Of
the rock masses that compose the in.
terror? An answer to this question 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 il
is assumed that its greatest density
cannot easily be less than from five to
ten times that of its superficial ma.
terialS, or twenty times the density Of
water. THIS being so, the rocks of tile
interior are either compressed to pro.
digious degree to give them this weight,
or they are of a different character
from those of the surface, possibly con.
tanning great quantities of metal. In
relation to this inquiry knowledge of
the exact density of the earth becomes
OF first Importance, and it is of special
interest to note that an extended series
or recalculations, made by Richarz and
Arlger- Menzel, extending back to the
year 1854, and with final results recent.
ly announced to the Berlin Academy of
Sciences, confirm within a very narrow
margin the earlier results obtained,
with less refined instruments. by Cav.
endish and his successors, through
period of upward of a hundred years;
these latest determinations fix the den.
sity Of our planet at 5.5O5 (comparel
with water).