Highland recorder. (Monterey, Highland County, Va.) 1877-1972, 1901-12-06
igARTH'S HOT INTERIOR
CAN tT BE UTILIZED AS A SOURCE
OF POWER2

Professor Mendenhall Thinks so-Increas-
fnr Temperature With Depth-modern
Scientists Don't Think the WORLDS
Centre Is q Molten Mass.
BY all odds the greatest amount Oh
mechanical power generated To-Day
for Industrial purposes comes from
burning coal. And inasmuch as the
unmined supply Of that material mas
Its limitations and is likely to De
used up inside of a couple Of centuries
IL not sooner, engineers and philoso-
pliers have begun to cast about Tor
other resources. The substitutes 1of
coal which are generally suggested
are falling water, the wind, sunshine
and the waves and tides. But FRO
lessor Il. G. Mendenhall, In easier
Magazine, makes q somewhat mover
addition to the list. Referring to the
interior heat of the earth, he says that
it lis worthy Of most serious consider
alton as q possible and reasonable
source Of power. Its Importance VIII
be greatly enhanced when we are able
to transform heat directly into cleo
tricity on large scale and with econ
omy, avoiding the great waste which
necessarily accompanies the use OF the
steam engine; and this must soon come
about"
The earth is a globe nearly 5000
miles In diameter, and except for a
thin shell, is probably hotter than any
furnace yet devised by human skill.
Estimates differ as to the thickness
Of this crust. Temperature increases
with descent, in mines and oil wells,
at an average rate of one degree Fab
renheit for every fifty or sixty feet.
Assuming that the mean for the
earth's surface is something like fifty
degrees above zero, the boiling point of
water (212 degrees) would be reached
at a depth of about 5000 feet. And 1t
Is believed that between thirty and
fifty miles down the heat is sufficient
to melt the hardest known substances
clay, lime, carbon and the like. 1t
would probably not be wide of the
mark to say that at this distance tenn
pera cures CT 5000 and 5000 degrees ex-
LIST.
The old notion was that the interior
of the earth was molten, and the phe-
nomena Of volcanoes tended to
strengthen that belief. Modern writ
ers, however, incline to the theory OF
potential Elasticity" That is to say,
they think that the heat there is ade-
quate to melt the most refractory
materials, but that melting does not
actually take place owing to the pres
sure Of superintendent weight.
A moments reflection will satisfy
one that If this source Of energy should
ever become available, it would vastly
transcend in value wind power, water
power, sun power and tide power.
Even the coal deposits Of the earth,
consumed and unconsumed, would be
lnconsiderable in comparison. Were
the internal heat drawn off by arti-
fetal means-the conversion into other
forms Of energy for mans use-the
cooling of the globe, which is already
going on, would be accelerated, and the
earth would be reduced to the cold,
dead condition of the moon a little
sooner than otherwise. Thus the very
existence of the human race might
possibly be abbreviated a few thou
sand years by climatic changes. Still,
If the great heat reservoir here under
consideration were once tapped in q
satisfactory manner, it would be
practically ineXhaustible bank account
to draw upon. AK.
Professor Mendenhall outlines no
plan for utilizing the earth's heat be-
yond a suggestion that it might be
converted directly into electricity
without the intermediate use Of steam.
There is much to commend this idea.
If it is necessary to go down 5000 feet
in order to make water boil, it would
be necessary to 60 down 1000 more
to generate steam at useful pressure.
say $50 to 200 pounds to the inch.
To be sure, were some more volatile
substance than water employed to pro-
duce the motive vapor, lower tenn
perature would suffice. This in the
principle Of a new motor in Germany
which just now threatens to work
revolution in power generation. 1t
takes the exhaust of condensing
steam engine, at temperature Of
about $50 degrees, vapOrizes Herewith
some sulphur diOxide, and thus gets
more than q third as much power as
the principal engine develops. This
heat would otherwise be wasted. A
sulphur dioXide engine might be run
successfully, so far as temperature
conditions alone are concerned, at a
depth of a mile, which has more than
once been attained by oil wells.
The principle of the thermo-electric
couple is very simple. When a change
Of temperature occurs at the junction
Of two slips Of dissimilar metals an
electric current is excited in them.
Many inventors have tried to turn
that phenomenon into account. Cla-
mond built up hollow cylinder out of
alternate layers Of tin and an alloy
containing anthony, and heated the
interior with gas fame around a
perforated earthenware tube. Harry
Darlington Cox, of Hartford, a few
years ago constructed a somewhat
similar battery, which could be run
with a gas jet and be left alone for
month at a time. The Postal Tele-
graph tested it and found that it would
work a telegraph wire. For some rea-
CON these and other thermO-electric