Fergus County argus. [volume] (Lewistown, Mont.) 1886-1946, 1906-11-09
Interior Condition of the Earth.

Interior Condition Of the Earth.
Few papers read before the British
Association for the Advancement of
Science have attracted such wide at
tention or aroused such warm discus
sion among physicists as the address
delivered by Mr.. r. j. Strut on Radio
Activity and the Internal Structure of
the Earth Lord Kelvin, the Nestor
OF British scientists, in letter pub
lished in the London Times protested
against the hypothesis that the heat
OF the sun or earth or other bodies
in the universe is due to radium."
and reasserted his conviction that
planetary and solar heat is due to
gravitation. When one recalls his
brilliant amplification of Helmholtz's
theory that contraction of the sun
amounting to about ten inches day
would be sufficient to account for it's
present heat, one can readily under
stand his position. On the other hand
We nave no more reason to suppose
that gravitational energy is responsible
for terrestrial and solar heat than we
have for attributing to radium the
temperature observed. The question
whether or not the sun is actually
shrinking can hardly be definitely an
swere for century or more
Struts calculations are certainly
plausible, even though we may not be
ready to accept his radium theories
entirely. The poorest igneous rock
which he examined, namely, Greenland
basalt, contains more than ten times
the proportionate quantity necessary
to uphold the assumption that the
| iy 40 al
Because there Is too much radium in
the earth, Strut has been forced to
the conclusion that the interior of the
globe does not contain radium. His
data for the quantity Of radium in
rock point to thickness Of at most
forty-five miles from the earth's crust,
and that the internal temperature at
the bottom Of the crust is about 1900
deg. G. To these views it may be
objected that the diffusion of radium
may have some effect on it's property OF
radiating heat. Indeed, Sir William
Crookes has tentatively shown that a
mOlecule of radium locked up in a mass
of rock and compressed in the inter
ior OF the earth would not throw off
the heat generating alpha particles,
but would remain in state of sus-
pended animation his data having
been obtained in experimenting with
powdered compressed pitchblende.
! To involve the problem still more,
we must take into consideration the
existence of thorium, uranium, and
other radioactive substances discov-
cred and undiscovered.
Curiously enough, Struts theory
necessitates an assumption of the in
ternal structure Of the earth, that is
quite in harmony with the prevailing
views OF biologists. Strut finds that
the inside nucleus heated by the crust
OF adium-containing material must lie
at uniform temperature of 1900 deg.
e. throughout, just as a loaf of bread,
which has been in an oven long
enough, acquires steady temperature
equal to that of the walls of the oven.
Struts crust would contain about one
thirtieth of the earth's volume, and if
throughout it the radium heat-energy
We're of the average of that exhibited
by many samples examined by him,
the temperature of the earth could be
maintained until our stores of uranium
suffered sensible depletion. Such an
assumption would lead to the conclu-
sion that the whole of the central
portion of the earth consists of non
radioactive substances at an approx
mate uniform temperature somewhat
below the melting point of platinum.
Prof. Griffiths has examined the
proofs of this supposition at our dis
poSal, and we here present a summary
of his findings.
Prof. George Darwin has stated that
the rightly of the earth is at least as
that OF steel. Hough arrived at sub
stantially the same conclusion by a
different method. To Oldham's mind
the evidence pointed to a central me-
tallic core and to the existence of
marked differences in the physical con-
stants OF the core and the surrounding
crust. Prof. Mines recent investi-
cations have led him to the conclusion
biased on the difference in the rate
of propagation of earthquake waves
that the material below a depth ap-
proximating to thirty miles is of uni
form, and that the change in physical
constitution is abrupt. Geodetical OBJ
servations conducted by means of
plumblines and pendulums have con-
WINGED Col. Burrard that we are not
justified in asserting the non-existence
or deep-seated variations in density
but that we are justified in believing
that the variations in density which
have been discovered are apparently
superficial.
The agreement of results drawn from
such dissimilar sources is certainly
striking. 1t is possible that the evil
dence from each source, considered
independently. might be regarded as
inadequate, but the cumulative effect
Is suflclently strong to justify the
belief that some marked physical
change in the constitution occurs at
1 depth of some thirty to fifty miles
AT all events, we have indications that,
with the exception of a comparatively
hin crust, the earth consists of a non
radioactive substance with a rigidity
approaching that of steel with an av-
arage temperature in the neighborhood
OF loo deg. C.-Scientific American
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